The crosstalks in detection circuits in the process of miniaturization for high-precision fiber-optic gyroscopes (FOG) become increasingly serious. In complex application conditions, it is difficult to measure crosstalks in the FOG output using traditional methods based on turntables. In this paper, we propose a method for measuring crosstalks based on simulated rotation rate phase ramp. We implement a specially designed circuit to generate a controllable phase ramp, combine it with a closed-loop phase ramp, and then connect the Y-waveguide using an adding circuit. This method can correctly estimate the crosstalk magnitude by testing gyroscope response. Related experiments are conducted, and experimental results show that the proposed method can realize the self-inspection of crosstalk in FOG detection circuits without turntables and improve the design and test efficiencies for application systems.