For the problem that the measurement precision of the rotation angle about line-of-sight vector of single star sensor is relatively low, a method of utilizing measurement from MEMS(micro-electro-mechanical system) gyro and two simultaneously operating star sensors to obtain accurate attitude knowledge of CubeSat was proposed. Based on the idea of averaging two quaternions, two attitude determination schemes called centralized filter and decentralized filter were drawn up by using MEKF(multiplicative extended Kalman filter). Simulation results indicate that attitude determination performance is improved effectively by the presented method and it has higher precision and quicker convergence, under the circumstance of utilizing low-cost and low-accuracy attitude sensors and traditional attitude filtering algorithm. It provides a feasible reference for low-cost and high-precision attitude determination of CubeSat, and has certain engineering application value.