This paper proposes an efficient triple-grid multiscale finite element method (ETMSFEM) for the simulation of groundwater flow in heterogeneous porous media. The main goal of this method is to improve the efficiency of constructing basis functions. It is accomplished by introducing an intermediate grid between the coarse grid and the fine grid. Instead of solving a local problem in a full coarse element, the ETMSFEM breaks the basis function construction problem down to subproblems in the elements of the intermediate grid. Hence, the computational cost can significantly be reduced and the accuracy can be ensured. For this reason, the ETMSFEM can save much computational cost in solving groundwater flow problems, especially for large-scale problems, long-term prediction problems, transient flow problems and nonlinear problems. Some numerical examples in this paper indicate that the ETMSFEM achieves almost the same accuracy as the MSFEM, while saving a large amount of CPU time.