The performance of cast-in-place cement concrete pavement can be greatly influenced by the surrounding environment and the quality of construction, and it requires longer curing time before opening to the traffic. The precast cement concrete pavement has the potential to address the disadvantages of using the cast-in-place cement concrete as the pavement surface material, and it also provides an alternative solution for the rapid repair of pavement damage. The current study aimed to assess the influences of geometry of full-scaled precast concrete slabs with various load transfer joint types. A numerical analysis was conducted using the finite element method to analyze the mechanical responses of the single and double slabs in accordance with the elastic thin-plate theory and the Specifications for Design of Highway Cement Concrete Pavement. Under the premise of determining the most unfavorable load position for different mechanical parameters, the mechanical response regularity under the critical loads was determined. The precast concrete pavement slab with dimensions 4 m long, 3 m wide and 0.28 m thick exhibited better mechanical responses when considering the maximum deflection and flexural stress as the evaluation index. The results indicated that the variation of joint forms has marginal influences on the maximum deflection and displacement transfer coefficient. When considering the maximum flexural stress and load transfer coefficient of the precast slabs, the circular tongue-and-groove joint form was recommended for application.