Finite element method is often used for solving unsaturated soil seepage problem. However

numerical difficulties such as slow convergence rate and inaccurate results are commonly existed in numerical analysis because of the highly nonlinear soil-water characteristic curve and hydraulic conductivity function. Based on a rational function transformation (RFT) method

a new temporal adaptive transformation method with under-relaxation (ATUR1) is proposed to solve the unsaturated soil seepage problem. It is shown that the transformation in ATUR1 can reduce the nonlinearity of solution profiles of the Richards' equation both spatially and temporally; thus the inefficiencies in the numerical solution process caused by these nonlinearities can be overcome. The under-relaxation technique can further increase the efficiency by curbing the oscillation tendency during iterations; and the temporal errors during the whole simulation can be controlled effectively by the automatic temporal adaptive scheme. Numerical examples show that the proposed ATUR1 method is a robust and efficient numerical method for practical unsaturated soil seepage simulation.