Abstract: Monorails have been typically used for agricultural transport in the steep, mountainous regions. The slope of the monorail can change rapidly in response to the undulating terrain. The driving load of the monorail transport vehicle can then change dramatically on the monorail slope. The agricultural monorail surface is also subjected to the monorail wheel and the surface rack between the engagement contact stress. The service life of the monorail surface can often require a variation in the load under contact stress. It is difficult to determine when the failure occurs. This study aims to explore the effect of the slope on the service life of the agricultural transport monorails. A monorail running load model was established to determine the traction force and speed of a monorail conveyor under different slopes. The optimal parameters of the agricultural transport monorail were selected to verify and test the meshing strength of the monorail wheel and the agricultural transport monorail surface rack. The test results show that the meshing strength fully met the requirements of the national standard. The mechanical drive transmission of the monorail was used for agricultural transportation. There was a meshing structure between the monorail wheels and the rack teeth on the monorail surface. A three-dimensional finite element (FE) model was established for the contact between the monorail wheels and the surface of the monorail. The rack material on the monorail (Q235A) was set as a typical structural steel. A bilinear constitutive model of the isotropic hardening material was selected to disregard the effects of temperature and strain rate. The monorail wheel shared a rotating connection, which was grounded to the wheel. Different connection torques were applied to the monorail wheel under the various slopes. A simulation was performed on the traction load of the monorail transport vehicle under different slopes. The rotation angle of the monorail wheel meshing rod was also adjusted via the monorail surface rack. Different positions of meshing contact were simulated on the same monorail surface. The contact stress and strain fatigue cycle of the monorail surface was then performed under monorail transport driving after simulation. The results show that the service life of the monorail surface of the agricultural transport monorail depended mainly on the size of the monorail slope. Once the rated load of the monorail was 500 kg, the maximum contact stress on the monorail surface of the monorail was 35.8, 147.5, 256.9, 307.9, and 314.5 MPa, respectively, on the transport slope of 0°, 10°, 20°, 25°, and 45°. The minimum number of strain fatigue cycles was >1.00×106, 7.84×104, 1.07×104, 6.07×10³, and 5.69×10³, respectively. The monorail slope was reduced significantly for the long service life of the monorail surface of the agricultural monorail. If the annual operation of 120 days, 10 carloads per day, and the maximum slope of the agricultural monorail railway over 25 °, the service life was determined to be 5 years for the fatigue defects in the agricultural transport monorail surface.