Abstract: This paper proves,in theory,that GDOP decreases as the number of satellite increases.Then the recurrence algorithm of GDOP and positioning solution is proposed based on the existing positioning software.This algorithm chooses the fifth satellite which enables GDOP₅ to be minimized from the surplus visible satellites and make use of the positioning information provided by this satellite to correct the four-satellite positioning solution.Finally,the method for choosing the fifth satellite is given.The purpose of the algorithm is to exchange the least amount calculation for the effective improvement of the positioning precision.