Abstract: To address the problem that the positioning performance of BeiDou navigation satellite system(BDS) single-frequency positioning degrades in an occluded environment, a triple-frequencies positioning model is introduced to increase the redundancy of observations, and an "ionospheric factor" is introduced to connect the observations of three frequencies from the same satellite in order to optimize the performance of triple-frequencies positioning. By comparing the single-frequency, dual-frequency and triple-frequency positioning results of BDS with the 24-hour measurement data among four sites, the results show the availability of the triple-frequency model is close to 100% in the BDS system at some sites, but the triple-frequencies model should not be used as an independent positioning model for the time being, may be used as an auxiliary positioning model for single-frequency or dual-frequency positioning. The results of positioning accuracy analysis show that the triple-frequencies model has less positioning advantage in the open environment but better positioning advantage in the occluded environment.