Abstract: The paper analyzed the reasons for the start slipping and belt floatation at the knick points of belt conveyor in main inclined shaft of Li jia lou coal mine . According to the analysis，the lower tensioning force of the hydraulic automatic tensioning device and the lower curvature radius of the concave arc of conveyer belt were the root cause of the start slipping and belt floatation of belt conveyor. Based on the theoretical analysis and test results，some improving measures were put farward，such as changing soft-starting time of belt conveyor，increasing the tension of the hydraulic automatic tensioning device and using press belt transshipment device at the knick points. The belt conveyor ran safely and reliably. It provided valuable practical experience for other mines to solve the similar problems.