Considering the influence of random uncertain factors,the reliability analysis for the working cylinder body of the 50MN three-beam and four-post forging hydraulic press is carried out. Using parametric design language ANSYS (APDL),the three-dimensional parametric model of cylinder body is established. According to the stress-strength interference principle,the reliability model of cylinder is constructed. Setting the geometry size,load and material strength of the working cylinder body as random variables obeying a certain distribution,using the ANSYS/PDS module and Monte-Carlo simulation technology,the paper analyzes the reliability of the cylinder body. Through the sensitivity analysis,the influence of the uncertainty variables on the cylinder body reliability is discussed. This study can provide a theoretical basis for the design of the working cylinder body of the forging hydraulic press,and it has important significance for the reliability research of the cylinder block.