This paper proposes a demodulation phase angle compensation (DPAC) for dual-mass MEMS gyroscopes with small frequency split (Δω) and low-quality factor (Q value), to reduce the quadrature interference on Coriolis signal output. The harmful contribution of quadrature error and demodulation phase angle drift to the gyroscope performances is analyzed and quantified. The quadrature stiffness correction (QSC) system based on DPAC is redesigned, and it was analyzed that the QSC would reduce the Δω and then affect the performances of the gyroscope. Wherein, the DPAC algorithm is implemented by a back propagation neural network. Finally, the experiments are arranged to verify the theoretical analysis. DPAC experiments were performed for both open-loop detection method and QSC method, respectively, for open-loop detection without DPAC (test 1), open-loop detection with DPAC (test 2), QSC without DPAC (test 3), and QSC with DPAC (test 4). The scale factor results based on these four tests are 15.384, 15.441, 16.652, and 16.731  mV  /  deg  /  s, respectively. When tests 2, 3, and 4 are compared to test 1, the bias stability results improved by 88%, 84%, and 97%, and the angle random walk improved by 28%, 23%, and 34%, respectively. Test 4 is proved to be the best type for bias performances, as is the case with a temperature range experiment from 60°C to −40  °  C, but the performances of its scale factor deteriorated. Moreover, the bandwidth is reduced by 4 Hz because of the QSC.