To measure the athletic information of exercisers, the applications of smartphone are programmed based on the sensing data from GPS device. These applications provide exercisers for running or walking distance, exercising time, calorie consumption, average speed, and so on. Among them, the exercising distance should measure accurately because it directly affects the other athletic information for exercisers. However, the existing methods for measuring the exercising distance makes errors because they are worked on the simple sphere or ellipse earth models. Actually, the surface of real earth is composed of inclined ground like hills and valleys. In this paper, a new exercising distance measuring algorithm is proposed to compensate the errors of existing method. It considers the altitude of slopes in exercising routes. To evaluate exercising distance measuring algorithms, we implement the athletic life-guide system based on the smartphone platform. In experiments, the proposed method shows that it provides more accurate distance measurement.