Knowledge Heterogeneity is the source of Knowledge Collaboration in Enterprise while the Virtual Practice Community constructed with Web 2.0 technology is a very important way to gain heterogeneous knowledge. Active Cross-border Innovation makes the virtual practice community to be heterogeneous knowledge preference nowadays. However, the appropriate degree of knowledge heterogeneity that can excite the community to be synergy equilibrium is difficult to seek. This paper studies on the signaling game analysis of knowledge heterogeneity in Virtual Practice Community based on two-period reputation model. We mainly analyze the lower bound of optimal interval of knowledge heterogeneity to reveal the management meaning of this optimal interval.