In order to understand the distribution patterns of permafrost in the Wenquan area on the Qinghai-Tibet Plateau, the effects of altitude, slope and aspect and other topo-climatic factors on the distribution of permafrost were studied, using the correlation analysis with digital elevation (DEM) data, borehole observations and measures from ground penetrating radar (GPR) and the electromagnetic sounding method. A permafrost distribution model based on the nonlinear multiple adaptive regression splines (MARS) method was developed, taking elevation and direct solar radiation as variables. Five-fold cross validation shows that this model has a good simulation capability in describing the permafrost distribution spatial pattern in the study area. Applying the model to the study area indicates that in the Wenquan area there is 1 881 km² of permafrost area, accounting for 76% of the total Wenquan area. The MARS model is better than the mean annual ground temperature model and the logistic model, because the MARS model takes into account not only elevation, the predominantly controlling factors in a mountainous area, but also solar radiation, which has adjusting effect to the permafrost distribution.