Phase quantization errors appear in phased array antenna utilizing the digital phase shifter for beam steering. And this cause relatively high parasitic side-lobes. This paper demonstrates the application of genetic algorithm (GA) in reducing the phased quantization errors effects on parasitic side-lobe level of phased array antenna. GA has the ability to escape from local minima and maxima and is ideally suited for problems where the number of variables is very high. The results of simulations, accomplished using the methods of random phase feeding and GA are presented in this paper.