Based on slip line field to give a simple and convenient graphic method it have great theoretical and engineering significance aiming at the problems of complex calculation method and large amount of calculation in tunnel stability analysis. Firstly, the method of the whole section slip line field at unsupported in loess tunnel was developed and improved. Secondly, the visual analysis program of the slip line network method is realized by MATLAB. Combined with the test results of the experimental loess tunnel collapse, the analysis program of the method of the whole section slip line field at unsupported in loess tunnel was verified. Finally, the influence of the internal friction angle and cohesion of the shear strength of loess on the collapse range of surrounding rock and the ultimate bearing capacity of soil arch in loess tunnel are evaluated.The results show that the ultimate bearing capacity of loess arch increases with the increase of cohesion also the sensitivity. The ultimate bearing capacity of loess arch decreases with the increase of friction angle then the sensitivity decreases, and the sliding range decreases with the increase of friction angle.