Silicon microgroscope is processed usually by microfabrication technology. It could lead to a quadrature coupling error and influence the output of the silicon microgyroscope for the lower relative accuracy from the fabrication processing. To optimize the structure of the silicon microgyroscope and enhance its performance, a theoretical model of quadrature coupling coefficients for the microgyroscope was established. Firstly, energy theorem was used to infer the in-plane stiffness of driving beam to set up the stiffness matrix of the microgyroscope. Then, the theoretical analysis model of quadrature coupling coefficients was established. According to a dual-mass vibrating silicon microgyroscope developed by our research group, the theoretical calculation shows that the direct coupling coefficient and the second-order coupling coefficient are 4.74×10-5 and 8.44×10-7, respectively, and the quadrature coupling coefficient of the developed microgyroscope is 4.75×10-5, 8.7% different from the simulation value. Meanwhile, the analysis indicates that the maximum value of quadrature coupling coefficient is 2.18×10-4 , 7.9% different from the simulation value. Finally, the calculating result is confirmed by an experiment test. It concludes that the theoretical model of quadrature coupling coefficients can provide the theory foundation and application direction for improving the properties of silicon microgyroscopes.