Abstract: The "Structural-Insulation" integrated composite wall panel (SIW wall panel) is a new type of grain warehouse wall element, which is composed of the inner, outer leaf concrete walls, and the insulation panel through the connectors. It can effectively improve the shortcomings of traditional bungalow brick walls, such as low bearing capacity and insufficient thermal insulation performance, as a composite structure with complex composition. The purpose of this work was to study the reliability of the mechanical properties of the SIW wall panel under the action of grain lateral pressure and the sensitivity of random parameters to the SIW wall panel, so as to better design and optimize the SIW wall panel structure. Firstly, a finite element analysis model was established and its validity was verified by tests. Meanwhile, the functional functions of different control conditions of the inner leaf wall deflection and the concrete strength were set as the failure criterion. Then the Monte Carlo Latin hypercube sampling and ANSYS finite element software were used to establish a stochastic finite element method. According to the distribution type, the random input parameters that affect the bearing capacity of SIW wall panels were substituted into the functional functions and then 100 000 sampling calculations were carried out. The failure probabilities for the two functions were subsequently calculated. They were used as a criterion for judging structural reliability against specifications. Finally, the sensitivity of all random parameters to the functional functions was quantified. In order to improve the reliability, it is necessary to control the variability of the parameters affecting the sensitivity of the structure failure and reduce its random dispersion. Meanwhile, the SIW structure can be optimized according to the parameters adjusting the positive and negative sensitivity. The results showed that the difference between the finite element simulation results and the test results was less than 5%. The failure probabilities of functional functions were P_f1=5.02×10^-2, P_f2=3.30×10^-4. The established finite element model was valid. The reliability of the failure probability of the two functional functions was within the safe range compared to the specification. When designing the SIW wall panel structure, the parameters that greatly affect the concrete strength failure should be mainly considered. The changes of grain gravity density, the elastic modulus of concrete, and the elastic modulus of insulation board had a significant influence on the overall reliability of the SIW wall panel. The research results provide a reference for the structural design, application, and optimization of the SIW wall panel.