The categories of evidence that are provided in criminal procedure law by using a special article are called ″the legal categories of evidence.″ Nevertheless， the definition or meaning of each legal category of evidence is not provided by law in the same way. The task of interpreting the concept of evidence categories is fulfilled by academic world of law. Among these academic interpretations， the ones in legal textbooks are undoubtedly most authoritative and typical. For a long time， scholars have nearly held the similar views on how to interpret the concept of evidence categories and current expressions of these concepts have been formed to affect the criminal procedure extensively. However， these current expressions deserve to be deeply rethought． The standard of distinguishing the categories of evidence by law is ″the presenting form of the evidence.″ The form of evidence depends on the concrete field of cognizing evidence that consists of the cognitive subject， the cognitive object and the cognitive range of time and space. Evidence may be presented in different forms in the different fields of cognition， and then must be classified into different categories. Therefore， the field of cognition must be the perspective or basic point of interpreting the categories of evidence. The traditional interpreting perspective of the legal categories of evidence is the field of ″general procedure″ in which investigation， prosecution and trial are integrated into a whole while interpreting the categories of evidence. From this perspective， materials of preserving evidence made by the organs dealing with the case， whether in written form or in electronic form， are regarded as the same categories as the evidence preserved. Not only is this view theoretically self-contradictory， but also it has obvious adverse effect on the judicial practice. First， it obfuscates the logical boundary between different categories of evidence， that is to say， the distinctions between documentary evidence or electronic datum and other categories of evidence are confused; Second， this view makes it difficult to confirm which category a testimony of witness should belong to; Third， it fosters the phenomenon of using evidence in written or electronic form during the criminal trial; Fourth， it makes the materials of preserving evidence made by the parties fail to be qualified for becoming evidence． The field of ″general procedure″ is essentially a varied field of cognition， for it can be divided into three second level fields of cognition that consist of investigation， prosecution and trial. The forms of the evidence are continually changing or transforming with the changes of the second level fields of cognition， and this is the primary cause of a series of dilemmas that traditional interpretation of the legal categories of evidence is faced with. As the field of trial has a key role in applying evidence， it should be separated from the field of ″general procedure″ and used to be the best perspective of interpreting the legal categories of evidence. Then， the perspective of interpreting the concept of evidence categories will be permanent fixed. The current reform of the system of criminal procedure provides an unprecedented opportunity for the perspective of interpretation to turn from the field of ″general procedure″ to the field of trail. If the perspective is changed， the traditional interpretations on each concept of the evidence categories should be amended， and the materials of preserving evidence should be classified according to the way of the evidence being preserved， but not the original type of the preserved evidence. Accordingly， the problems that the traditional interpretations on the legal categories of evidence are faced with will be smoothly solved: the logical dilemma between different categories of evidence will be broken; the phenomena of using evidence in writing or electronic form during the criminal trial will be further decreased; and， the materials of preserving evidence made by the parties will acquire the same status of being evidence as the documents made by organs dealing with the case．