Open innovation requires enterprises to search knowledge externally, but existing researches on the balance of binary knowledge search are insufficient. In order to identify the dynamic matching rule between binary search balance and developmental phase of SMEs, this paper divides the external knowledge search into two modes: proactive search and reactive search, and then it explores empirically the impact of the balance between these two search modes on enterprises’ innovation performance. The results show that the balance of binary search has a significant positive impact on innovation performance, but the most appropriate patterns for enterprises’ initial stage and growth stage are different. In the initial period, there is no complementary effect between the two types of knowledge search, either too balancing or too different between the two search modes is not conducive to enterprises’ innovation performance. But in the growth period, there is a complementary effect between the two modes of knowledge search, the higher the degree of balance, the better the innovation performance. According to the above results, this paper discusses the optimal balance pattern for different stages, namely enterprises in the start-up period should choose the mode of “punctuated balance”, and after entering the growth period, the enterprise needs to transform the mode into “simultaneous balance”.