The fiber positioner of LAMOST is used to realize the accurate positioning of optical fiber in the process of astronomical observation. However, the existence of various error sources can affect the position accuracy of the fiber, and cause the actual results cannot satisfy the requirement of precision. In this paper, a fiber positioner is taken as research object, and the sources of positioning error, including mechanism error and joint clearance, are taken into consideration. The corresponding error model is established based on Monte Carlo numerical simulation method and virtual prototyping technology respectively, and the impact of different error sources on positioning accuracy of fiber positioner is analyzed. The results show that when only considering mechanism error, the mean positioning error of the fiber positioner is small, which can satisfy the requirement of the observation accuracy. Furthermore, when the clearance between journal and bearing is considered, there is a deviation between fiber’s actual trajectory and ideal trajectory. With the increase of clearance, the deviation is becoming larger and larger making positioning accuracy of the fiber positioner worse even cannot meet the requirements of precision. The above analysis provides a theoretical basis for the design of a new generation of high precision fiber positioner in the future.