The reasonable estimation of the number of pavement works in the feasibility study stage of highway engineering construction project is one of the basis for the preparation of investment estimation. The selection of pavement structure layer and the calculation of thickness, the calculation of different terrain and pavement area is the main content of highway pavement quantity calculation in mountainous and hilly area. It is of great significance to select the correct calculation method according to different geological conditions. Through 10 engineering cases analysis, the paper analyzes the thickness and area calculation of the pavement structure of the mountain road. It is concluded that the pavement structure layer can be in the form of subbase + base + seal + surface layer. The influence of shoulder, subgrade retaining wall and middle separation zone should be considered in the calculation of pavement area.