Algorithm of multipoint-pump model based on high-power fiber laser is studied. An fast approximate solution is derived by analyzing the characteristics of multipoint-pump model. This solution can quickly calculate the laser and pump power distribution along the fiber and the output power. The result of the percentage error is about 1% and up to 0.2%. The working time of approtimate fast algorithm is 2%~17% of that of numerical algorithm. The fast approximate solution solves the problem of long computing time and large amount of computation in the numerical solution. The model can be quickly and accurately used for the laser design and optimization of pumping.