We propose a simple pumping method to increase the effective population of cold atoms in the clock state and in-vestigate the factors which affect the pumping efficiency in cold atom systems.We report the theory and demonstrate the corresponding experiment in an 87Rb integrating sphere cold atom clock.The experimental results show that the population of cold atoms in the Zeeman sublevel |F =2,mF =0〉 is approximately 1.62 times that of the result using optical pumping alone.This method can also be applied to increase the effective population in any one of the target Zeeman sublevels in other cold atom systems.