Unaided cold start time is an important performance of spaceborne global position system(GPS) receiver. Reduction of cold start time was developed for C/A code navigation receiver on low earth orbit(LEO). The search method of frequency and code phase, signal detector and parameters select, doppler bin, and code search speed were analyzed. Doppler bin of 500?Hz and code search speed of 475 chips/s were obtained. The orbital inclination, orbital altitude, elevation of GPS antenna and orbital eccentricity were researched as the influential factors to doppler range. GPS satellite allocation according to statistical information of angle between GPS satellites was discussed. Analysis and simulation shows that the cold start time is reduced by 25%~30% through this GPS satellite allocation method, the influential factors of doppler range are orbital inclination, orbital altitude, elevation of GPS antenna and orbital eccentricity in regular order with an effect, the cold start time is reduced by 25%~40% farther considering these influential factors of doppler range.