Basic positioning methods in GNSS receivers are based on code and carrier phase measurements. In this paper, the carrier phase measurements are considered. They are highly accurate, but limited with integer ambiguity, which is very important. This paper proposes an algorithm to resolve this problem. In addition, it shows the main factors that affect the accuracy of user position. To reduce the user's position errors, it eliminates the satellites with small evaluation angles and in the calculation, two weight models are proposed and applied. As compared to the positioning solution without weight, the positioning accuracy is improved by about 42.89 % with the SIGMA model and about 53.19 % with the exponential model.