Abstract: The results of the fields experiment in Hexi region in Gansu show that the sequence of nitrogen， phosphorus and potassium affecting the cotton yield is P>K>N from 172.5 kg/hm2 to 241.5 kg/hm2 of N， Phosphorus and nitrogen are more important factor effecting the cotton boll number per plant than potassium and potassium is an important factor to the cotton boll weight. The proper proportion of N, P2O5 and K2O in Hexi region of Gansu is 1:0.67:0.23.