Abstract: Conveying inclination is the key difficulty in the design of straight-line climbing section of pipe belt convey-or. Expansion accidents occur during assembly if the inclination is too large. It will be necessary to re-layout the pipe-line if the inclination is too small,so that the cost of the whole machine will increase significantly. In this paper,the relative slip theory is used to build a mechanical model of the material in the pipe. The friction coefficient is used to characterize the slippage between the material and the pipe. The relationship between the friction coefficient and the ultimate transport angle under different loading rates is deduced. Then,the transport inclination of the belt conveyor under three typical filling rates of 50% ,62% and 75% were analyzed,respectively. The coefficient of friction coeffi-cient and the transport inclination angle were derived. According to the relative slip between the material and the tube, the ultimate conveying inclination of the belt conveyor are determined as 32°,34° and 36°,respectively. The method has some reference values for the design and analysis of material conveying inclination in the straight line climbing section of pipe belt conveyor.