Abstract: In response to the lack of platforms for online finite element calculation that can be easily accessed through Web browsers and perform efficient computing in Web browsers using local computing resources, a method of online finite element calculation based on WebAssembly and WebGPU in Web browsers is proposed. In the process of solving finite element systems, preconditioned conjugate gradient method, the way a coefficient matrix is stored and the parallelization of preconditioned conjugate gradient method on GPU platform are discussed and the key algorithm is determined. WebAssembly and WebGPU are used for programming and establishing a platform for online finite element calculation. Finite element models with different element and node number were selected for numerical experiments of heat conduction calculation and structural calculation. The results demonstrate that in the Web browser, the computing efficiency of serial finite element calculation based on WebAssembly is close to that of native C++ program and the parallel finite element calculation based on WebGPU shows a speedup of two orders of magnitude in solving million-dimensional systems, which achieves online efficient computing.