In order to improve the precision and efficiency of sparse optical phased array, 1×16 optical phased array was designed based on silicon-on-insulator(SOI) platform by using the structure of spaced cosine distribution of output waveguides. Combining the effective refractive index method and 2-D finite difference beam propagation method, the far-field intensity distribution was simulated. The results show that, the side lobe suppression ratio decreases to 41.46% from 89.72%, and the full width at half maximum of the main lobe is compressed to 0.81° from 1.20°. This design method can significantly suppress the grating lobes and further compress the main lobe, and has a promising future in the field of beam deflection, such as robot obstacle avoidance, pilotless, target detection and so on.