Abstract: In order to guide the model test fillers and improve the test accuracy, the mudstone similar material was selected to make samples, and the effects of three factors affecting the filling process of model test on the mechanical properties of mudstone similar material was studied. The analysis results show that when the number of layers increases from 1 layer to 5 layers, the uniaxial compressive strength, elastic modulus and tensile strength of similar materials are reduced by 23.80%, 32.0% and 20.83% respectively. And the compaction times are increased from 1 to 5 times, the uniaxial compressive strength, elastic modulus and tensile strength of similar materials increased by 15.00%, 28.61% and 6.76%, respectively. Compared with the interface treatment method of rough treatment, the uniaxial compressive strength, elastic modulus and tensile strength respectively increased by 14.25%, 22.63% and 7.99%when gypsum was sprayed on this basis. The multiple linear regression equation between the mechanical properties of similar materials and the influencing factors of packing process is established. Combined with the test results and equations, the model test fillers can be guided, the mechanical properties of similar material can be prevented from decreasing, and the test accuracy can be improved.