To improve the bias stability of a silicon microgyroscope for more precise applications, the optimization of bias stability for the silicon microgyroscope was explored. By taking a typical Z-axis silicon microgyroscope for an example, zero-rate output errors of a typical Z-axis silicon microgyroscope caused by mechanical coupling, electrical coupling, mechanical thermal noise and interface circuit noise were analyzed. On the basis of decreasing the drift and noise of zero-rate outputs, the design principle to improve the bias stability of the silicon microgyroscope was proposed. The mechanical structure and interface circuits for the silicon microgyroscope were designed. To verify the availability of the design principle, the bias stability of the silicon microgyroscope was tested. Experimental results indicate that the zero-rate outputs of four tested silicon microgyroscopes are no obvious drifts, and their bias stabilities are at the level of 6 (°)/h. It suggests that the proposed silicon microgyroscope has reached a medium tactical precision grade.