The invention discloses a method for monitoring wearing capacity of a shaft housing of a submerged roller. By the method, a grate arranged above a coating boiler is provided with a displacement sensor for detecting the horizontal position of some a point of band steel, then a signal is converted into a measured value D of the horizontal displacement value of a measured point of the band steel through a displacement changing and transmitting device, then the measured value D of the horizontal displacement value is transmitted to a computer system, and finally the computer system outputs the measured value D of the horizontal displacement value in real time and compares the measured value D of the horizontal displacement value with a set value in the computer system, the set value is a theoretical value y of the horizontal displacement value of the measured point of the band steel, the theoretical value corresponds to some a value of the wearing capacity A of the shaft housing, and when the horizontal displacement value D is not smaller than the y, the computer system make a corresponding response. The invention can accurate judge the wearing condition of the shaft housing of the submerged roller, and the operating staff obtain the wearing condition of the shaft housing of the submerged roller according to the response made by the computer, thereby reasonably arranging and using the submerged roller.