Act-utilitarianism is a traditional form of utilitarianism, while rule-utilitarianism introduces new contents into the modern form of utilitarianism, thus refreshes this theory. As a representation of teleology in moral philosophy, utilitarianism is an important theory and has great effects on human life. However, problems and difficulties still exist, such as the debate between act-utilitarianism and rule-utilitarianism. On one hand, rule-utilitarianism brings new problems and difficulties to the calculation of utility; on the other hand, it also plays a significant role on the relationship between deontology and utilitarianism, to which act-utilitarianism does not consent.