The invention relates to a vacuum assisted gravity pouring fuse cast thin wall casting method. It fixes the baked fuse mold casting shell inside the container with sealing device between the shell and the container, capped the top cover of the container, adjusting the fixed device, forming enclosed space between the shell and the container, turning on the heating device to retain the temperature requirement if necessary, turning on the vacuum system to establish the vacuum degree, pouring metal fluid into the cavity after the generation of negative pressure inside the shell, closing the vacuum system, release the vacuum, cleaning the shell to get the complete casting piece. The equipment structure is simple, small in investment, convenient in operation, being able to improve the final product rate of the thin wall casting piece and metal utilization rate to reduce production cost.