In order to study the influence of humidity, loading, freezing and thawing effect of three axis shear strength of the Loess in Luochuan, using the GCTS electro-hydraulic servo dynamic testing system of low temperature and high pressure three axis, the different moisture content, freezing conditions, the three axle shear experimental melting conditions, the effects of moisture content, loading, freezing, melting effect on joint action the strength of loess and its mechanism. The experimental results show that the strength characteristics of soil water through the effect of coupling to the soil particle changes of loess, frozen through the phase transition temperature of free water in the soil freezing soil, change the external force structure, and thus affects the strength of soil, thawing effect is mainly due to the freezing process of soil water volume expansion on soil particle joint the damage and destruction, so that the strength of loess will greatly decrease.