Dynamic population process of ErP5O14 crystal described by rate equations is reported in the present manuscript. All dynamic process and pumping power influence have been calculated out for ErP5O14 crystal when excited by 650nm laser. Established rate equations has included spontaneous emission rates, absorption of pumping photon, relative stimulated emission rates, nonradiative multiphonon relaxation rates, all possible energy transfer rates and back energy transfer rates. It is found that upconversion luminescence intensity is very strong and upconversion luminescence behaviour is very good when 650 nm laser pumping power reaches 103～105 W. The stable population probability of 4I15/2 state can be reduced to 0.0617 small extent. The population probability of 4F9/2 state can be first enhanced to 0.362 fast and then reduced to 0.0374 stable value smoothly. It means that the population of 4F9/2 state has been upconversioned to higher level. The very good results have emerged at that the population probability of 4S3/2 state may be as high as 0.212, which will results in the strong 543 nm upconversion luminescence. It is more significant that the population probability of 4G9/2 state may be as high as 0.160, which will results in the strong 379 nm upconversion luminescence.