Preliminary structure of light rail vehicle (LRV) carbody made of steel was designed considering its usage, strength, manufacturing, etc. Based on the finite element analysis, the optimization of design parameters associated with thickness of LRV carbody is carried out to increase the whole strength of the carbody and to reduce its mass. With the aids of the substructure technique and the modified technique with discrete variables in the optimization based on the finite element method, the consumed computing time is reduced dramatically. The optimized LRV carbody is re-analyzed by FEM to obtain its static strength and vibrating mode and is manufactured. The mass of the optimized carbody reduces about 1.3 kg, and the relative reduction ratio is about 10%. Then, the strength test of the real carbody under the static load is executed. It is shown by the numerical and test results that the design requirements of the LRV carbody are satisfying. The newly designed carbody is used in the LRV, which is the first one used commercially developed by China independently. Nowadays, the LRV is running on the transportation circuit in Changchun of China. Preliminary structure of light rail vehicle (LRV) carbody made of steel was designed considering its usage, strength, manufacturing, etc. Based on the finite element analysis, the optimization of design parameters associated with thickness of LRV carbody is carried out to increase the whole strength of the carbody and to reduce its mass. With the aids of the substructure technique and the modified technique with discrete variables in the optimization based on the finite element method, the consumed computing time is reduced dramatically. The optimized LRV carbody is re-analyzed by FEM to obtain its static strength and vibrating mode and is manufactured. The mass of the optimized carbody reduces about 1.3 kg, and the relative reduction ratio is about 10%. Then, the strength test of the real carbody under the static load is executed It is shown by the numerical and test results that the design requirements of the LRV carbody are satisfying. The newly designed carbody is used in the LRV, which is the first one used sold developed by China independently. Nowadays, the LRV is running on the transportation circuit in Changchun of China.