This paper presents a mechanical model for a polysilicon double-ended tuning fork (DETF) that is implemented as force sensor. This sensor is integrated into a compliant, passive microgripper utilized in a microassembly of 3D MEMS structures. An expression for resonant frequency of DETF is derived. Theoretical model is introduced to analyze the quality factor (Q-factor) of the resonator. The DETF is found to have a maximum Q-factor of 863. In addition, the characteristics of the snap-fit interlocking mechanism are modeled analytically. An optimization scheme is employed to determine the optimal dimensions that provide a maximum reliable amplification factor (A-factor) of the microleverage mechanism. Based on the simulation, the maximum A-factor is 26.12. The model presented here permits a gauge factor (i.e., sensitivity) of 5000 ppm/μN at compressive force of 80μN and A-factor of 25. The superior results obtained support the feasibility of DETF as a resonant force sensor for microgripping applications.