The fracture mechanism of fan blades in the subway system is analyzed by using the finite element method (FEM) and some experiments. Firstly, the mechanics performances of blade materials are obtained on the basis of the hydraulic testing machine. Then, the fracture surface of blades is measured with a scanning electron microscope (SEM). In the end, the natural frequencies of rotation blades are estimated by the means of nonlinear FEM program. It is shown from both the experiment and simulation results that the mechanics performance of blade materials is lower than its national standard, which is due to much bigger gaps and some inclusions in the cast fan. When voltage rises, the 79th natural frequency of blades becomes too approaching the rotating speed of fans easily to resonate. The biggest stress location of fan blades caused by centrifugal force, wind load and resonance is consistent in the fracture place, so the design of fan blades should be improved and optimized for preventing fracture.