Based on probability and mathematical statistics, a new method was proposed by analyzing the information of measured geometric position deviation of selected joints and by using truncated Gaussian distribution model to simulate the distribution of the geometric position of unmeasured joints.With the Monte-Carlo method, a group of stability factors was obtained, and the critical stability factor was determined with the probability theory.Furthermore, the critical stability factor calculation flow chart of existing reticulated shells was given.By taking a Kiewit single layer reticulated shell as an example, the feasibility of this method was verified.