The invention provides a vehicle tray assembly for installing a power battery. The vehicle tray assembly comprises a tray bottom plate and an installation cross beam, wherein the installation cross beam is arranged around the tray bottom plate, the tray bottom plate comprises at least one sub bottom plate, the sub bottom plate comprises an upper plate, a lower plate and a buffer cavity, the buffer cavity is arranged between the upper plate and the lower plate, and cooling fins are arranged at a lower surface of the tray bottom plate. In the vehicle tray assembly for installing the power battery, provided by the invention, the buffer cavity can have a good buffer effect during the travelling process of the automobile and when collision occurs, the influence of collision on the power battery is reduced, and the application safety of the power battery is improved; meanwhile, a runner or other assemblies also can be arranged in the buffer cavity, the safety performance is improved, and the space is also saved to a certain extent; and moreover, due to the arrangement of the cooling fins, heat transferred from the tray bottom plate can be dissipated very well by an air-cooling mode during the travelling process of the automobile.