For the combined action of inner and external factors , the high nonlinearity of the effective variables appears in dam safety monitoring such as jump - gradualness - jump phenom
ena, which brings about much trouble in analysis. Based on the threshold idea of threshold regression model, the threshold factors and threshold values are introduced and determined by the correlation analysis method of best curve fitted in conventional regression model. It is proved by an illustration to be available with satisfactory results in practical application of dam safety monitoring.