Abstract: Many collapses of high falseworks have occurred in recent years. The research on the design method of load and resistance factor for high falseworks is not efficient in spite of the lower standard of quality acceptance and the larger discreteness of load compared with those of permanent structures. Thusly, high falseworks with couplers (HFC) with height of 7.6m to 14.0m are taken into account. A simplified nonlinear calculating method of ultimate capacity is suggested and the statistic characteristics of model uncertainty are estimated by comparing the full-size test capacities to the predictions. In the range of tolerances given by the code, the statistics of uncertain parameters are obtained based on the samples collected in construction fields, test data and tolerances given in the code. The ultimate capacity statistics of 10 typical HFCs are estimated through 1000 Monte Carlo simulations. The optimal factors of load effect and resistance are found in terms of Enumeration Method. Design results given by the methods, and the British Code as well as the Chinese Code are compared. The results can provide a theoretical foundation for a new code.