In the dynamic environment, cooperative innovation has become increasingly important for firms to cope with the increasing speed, cost, and complexity demands. Most of the extant literature has focused on collaboration with suppliers, customers, universities and research institutions, etc. By contrast, little research has been engaged in firm-competitor relationship and its effect on innovation performance. Moreover, the limited studies on these relationships have drawn inconsistent conclusion which may cause confusion. The aim of this study is to examine how firm-competitor relationship affects focal firms' innovation performance. It analyzes the effect of firm-competitor relationship strength and relationship quality on focal firms' innovation performance. In addition, it considers the moderating effect of environmental dynamism. A series of hypotheses concerning these relationships is put forward based on relevant theories and literature. This paper, which reports the results of an empirical investigation based on data obtained from a random sample of Chinese manufacturing firms, will provides new findings.