In order to study the influence of longitudinal slope on the mechanical response of steel deck pavement, a method of slope-modulus transformation was proposed for the mechanical analysis of the steel deck pavement based on the time-temperature equivalence principle. Considering the mechanical action on a slope, a finite element model of the deck pavement was established to determine the critical load position of tensile and shear stress of the steel deck pavement. Additionally, the influence of longitudinal slope on the mechanical response of the deck pavement under the conditions of uniform speed and emergency braking was analyzed. The results indicate that the maximum transverse tensile stress at the pavement surface and the maximum transverse shear stress at the pavement bottom are always greater than their longitudinal counterparts under uniform speed. Under emergency braking, however, the critical slope gradient of the maximum transverse and longitudinal tensile stress at the pavement surface is 6%. The maximum longitudinal shear stress at the pavement bottom is always greater than the maximum transverse shear stress. This study is helpful in the structural design of large longitudinal slope steel deck pavements.