Human error is recognized as the major cause of structure failure. In this paper, the authors simulate human error in the process of structural design, manufacture, assembly and erection, and investigate statistically the influence they have on the structure's behavior. A 6×6 square plan double-layer space truss is designed and used as an example. A computer program is written to analyze the truss structure, with the ability to realistically simulate member buckling and to automatically adjust the displacement increment. The Monte Carlo method is used with trial number set to 100. The fully intact truss, and groups of trusses with either design errors, assembly errors, or variations in member strength, are analyzed and investigated statistically. It is found out that human error has a much bigger influence on the behavior of double-layer grids than member strength variation, and for the standard deviation of the structure strength, the influence of these two factors is shown to differ at least by a factor of 6.