In this paper, a new independently sensitive micro-electromechanical system (MEMS) thermal expansion-flow gyroscope is proposed and its sensitivity mechanism is revealed. A three-dimensional model of the structure was created using the COMSOL multiphysics simulation software and finite-element calculations of the temperature field of its sensitive structure were performed. The computational results show that at a 50 mW heater power and an angular-velocity variation range of -10 rad/s-10 rad/s, this gyro has a gyroscopic effect with a temperature sensitivity of 0.224 K·(rad·s^-1)^-1 and a nonlinearity of 2.37%, and a sensitivity of 1.8 mV·(rad·s^-1)^-1 and a nonlinearity of 2.06%. This gyro has a high sensitivity and simple process. In addition, this study lays a theoretical basis for subsequent structure optimizations.