In view of the problem that the sliding bearing of fuel gear pumps is prone to wear due to the thin oil film thickness under high load and high speed conditions, considering that the clearance ratio is the main factor affecting the minimum oil film thickness of the sliding bearing, the sliding bearing of a fuel pump was taken as the research object, the bearing capacity, minimum oil film thickness, pressure and temperature distribution under different clearance ratios were analyzed by PumpLinx software. The flexible deformation of the gear shaft of the fuel pump was analyzed. Then the relationship among the clearance ratio of the sliding bearing, the minimum oil film thickness, and the bearing load-bearing capacity was analyzed under the two working conditions of the minimum and maximum speed. Besides, the distributions of temperature, circumferential and radial pressure of the bearing were analyzed. The results show that the bearing capacity increases with the decrease of oil film thickness under the same clearance ratio, the decrease of the clearance ratio, or the increase of the rotating speed. In addition, regardless of the pressure distribution or temperature rise, it is the best when the clearance ratio between the gear shaft and sliding bearing is the smallest.