New product diffusion has long attracted the attention of both industrial practitioners and academic researchers .However,most of the literature is based on first-purchase analysis rather than on repeat purchase study .In fact,repeat purchase may have strong influence on new product diffusion in terms of diffusion scale and diffusion speed .As such,it is worth noting that in the literature,researchers disagree about the influence of repeat purchase on diffusion scale . We argue that such disagreements can be largely attributed to the neglect of the impact of product attribute .In addition,the influence of repeat purchase on diffusion speed is much less examined in the literature .Thus,this paper attempts to simultaneously investigate the impacts of repeat purchase on diffusion scale and diffusion speed,as well as the potential moderating effect of product complexity on the relationship between repeat purchase and new product diffusion . In doing so,we use Netlogo 4.1.3 to establish a multiple-agent model with a scale-free network structure based on the model in Peter van Eck,Wander Jager and Peter Leeflang (2011) .This model extends the basic model in the following aspects .First,we introduce the perspective of product complexity into the analysis of the influence of repeat purchase on new product diffusion .Second,by incorporating the negative effect of word-of-mouth and the dynamic process of knowledge transfer in new product diffusion,we employ a three-stage model to simulate the adoption behavior of new product users .The three stages are realizing the emergence of new product,deciding whether to take the new product,and deciding whether to make repeat purchase or to stop new purchase and spread the negative effect by word of mouth .Third,we include both informational influence and social influence in our modeling . The results reveal several interesting findings that are different from those in prior studies . First,on the one hand,although prior studies claim that the scale of new product diffusion increases with the higher rate of repeat purchase,this study finds that while repeat purchase does increase the diffusion scale,such a positive effect is not linear,i .e .,the influence of repeat purchase on the diffusion scale does not increase significantly when the rate of repeat purchase increases .On the other hand,at low levels of repeat purchase rate,the increase of repeat purchase may not be positively associated with the increase in diffusion speed .On the contrary,in the scenarios where the levels of product complexity are high,the increase of repeat purchase can even lead to the decrease of the diffusion speed .Second,this study reveals the importance of product complexity for new product diffusion .The influence of repeat purchase on diffusion scale will become stronger as the product complexity increases .By contrast,with the increase of product complexity,the influence of repeat purchase on diffusion speed will become less significant .What is more,lower levels of repeat purchase have a negative impact on the diffusion speed .On the whole,the results imply that the breadth of adoption (in terms of networking effect) is more decisive to the diffusion of new products with high levels of product complexity,whereas the depth of adoption (in terms of repeat purchase) is more crucial to the diffusion of new products with low levels of product complexity .