In view of the imperfection of the calculation method of horizontal frost heaving force in the design of L-shaped retaining wall in permafrost area, based on the Lifkin foundation model and the cooperative deformation principle between retaining wall and soil, a simplified calculation model of horizontal frost heave effect of L-shaped retaining wall with or without soil replacement behind the wall is established, and the proposed calculation model is solved by superposition principle and finite difference method. Furthermore, the water-thermal-mechanical coupling analysis software is developed by MATLAB. Combined with an engineering example, the horizontal frost heaving force obtained by using the proposed calculation method is compared with the field measured value, the corrected earth pressure value, the code empirical value and the simulation value of the coupling software. The results show that: (1) the horizontal frost heaving force obtained by the proposed calculation method is in good agreement with the field measured value and numerical simulation value, while the corrected earth pressure value and the code empirical value underestimate the effect of horizontal frost heaving force on the retaining wall; (2) compared with the code empirical value and field measured value, the horizontal frost heaving force obtained by the proposed calculation method presents two distribution modes of parabola and trapezoid along the wall height, which is more general; (3) the multifield coupling analysis shows that the frost heaving force trend obtained by the proposed calculation method is similar to the trend obtained by the coupling method, which indicates the feasibility of the calculation method and can provide some theoretical support and guidance for the design of L-shaped retaining wall in permafrost area.