Abstract: To overcome the shortage that GPS-RTK can not obtain centimeter level high precision positioning results due to signal blockage, insufficient satellites number and other reasons under complicated environment, in this paper, the tightly combination of ultra-wide band (UWB) short-range high precision positioning system and RTK are studied to improve the precision of dynamic positioning under complicated environment. According to the principle of UWB, the mathematical model of GPS-RTK/UWB tight combination is presented, and the data processing flow is introduced in detail. The experimental results show that GPS-RTK/UWB tight combination can further improve the ambiguity fixed success rate and dynamic positioning precision compared with only GPS when the observation environment is well. In a complicated environment with a cut-off mask elevation angle of 40 degree, the ambiguity fixed success rate was significantly increased from 20.93% to 93.96%. The positioning precision of N and E directions are improved to centimeter level, and that of U directions is improved to decimeter level, which can still meet certain engineering measurement needs.