The overall steering efficiency (OSE) of the liquid crystal optical phased array (LCOPA) is defined as the ratio of the first order diffraction’s intensity and the incident intensity. It is affected by many factors. A numerical analysis model is established to analyze the OSE. The model regards a LCOPA as the combination of a phase grating and an amplitude grating, and thus, model parameters include not only the geometric structural parameters but also the parameters of the phase profile. The general relations between the OSE and three kinds of factors, i.e. steering angles, the parameters of the LCOPA and errors between ideal and practical phase profiles, are studied. Ways to improve the OSE are proposed as well. Results show that increase of steering angles reduces the OSE while raising fill factors and reducing the pixel size can improve the OSE. Proportional spacing pixels are not the optimal distribution for improving the OSE, for which the method of finite-difference time-domain (FDTD) should be used to design the optimal pixel distribution. Reducing the space of two adjacent phase shifters and raising the phase reset value can improve the OSE obviously.