To address the strong coupling between the structural parameters of micro-electromechanical systems (MEMS) gyroscope and the electrical parameters of capacitive readout circuit, which limits the improvement of the output signal-to-noise ratio (SNR), this paper proposes a mechatronic integrated modeling and force-electrical co-optimization approach for a fully decoupled tuning-fork resonant MEMS gyroscope. An electromechanically-coupled dynamic model of the fully decoupled microstructure with dual-mass anti-phase drive and differential sensing, and a noise model of the capacitive readout interface circuit, are established. Analytical expressions for the equivalent stiffness of the decoupling beams and the structural modal frequencies are derived. The influence of structural dimensional parameters and circuit impedance parameters on signal noise is systematically analyzed. The critical beam dimensions of the microstructure and the capacitance/resistance combinations of the capacitive readout circuit serve as optimization variables, with the SNR as the optimization objective. The method of moving asymptotes (MMA) is employed to perform co-optimization of the electromechanical parameters of the MEMS gyroscope system, achieving an SNR improvement from 17.70 to 37.45 dB. Based on the optimized results, a printed circuit board (PCB) is designed for performance characterization and on-vehicle road test of the fabricated MEMS gyroscope. Experimental results show that the drive-mode and sense-mode resonant frequencies are 8 750.47 and 8 828.63 Hz, respectively, with errors of approximately 2.9% relative to theoretical predictions. Using the half-power bandwidth method, the quality factors (Q) of the drive and sense modes are measured to be 1 008.1 and 1 027.8, respectively. Single-axis rate-table tests yield a sensitivity of 0.486 9 mV/(°/s) and an SNR of 36.31 dB, with an error of about 3% relative to theoretical values. The zero-bias instability calculated by Allan deviation is 28.26(°)/h. Under typical dynamic driving conditions, including vehicle turning and roundabout maneuvering, the angular rate output exhibits good consistency with a high-precision reference gyroscope, thereby validating the effectiveness of the proposed electromechanical co-optimization design method from a system-level application perspective.