Mobile Guiding System for Parks based on highly precision electronic map is of many researchers' concern, but commercial software cannot perform GPS positioning on custom-made maps for parks, and is not accurate enough to satisfy the requirements for drawing high precision electronic maps. This study uses trajectories measured by My Tracks software and a map edited in JOSM software to implement a custom-made electronic map. By processing GPS data gathered by smooth filtering, k-mean algorithm, mean filtering, and weighted-averaging (SKMW), it calibrated a custom-made map for a park mobile guiding system, based on a design from the gvSIG Mini open source project. Using Beijing JiuFeng National Forest Park as a case, this study developed LBS and SNS related service functions. The field test shows that the SKMW method can effectively improve the accuracy of a custom-made electronic map, and the practicality and expandability of a park mobile guiding system.