The invention discloses a calibration method of X-ray generator tube current. The method comprises the following steps of dividing an initial characteristic curve of pipe current-filament current into N sections, using a straight line to connect two end points of each section of the curve, and calculating an equation (Yn=knx+b) of each section of the straight line, wherein kn represents the slope of the nth section of the straight line, n=1,...,N, b is a constant, x is a pipe current value, and Yn is a voltage value of the filament current; collecting the pipe current value of the two end points of each section of the straight line and the corresponding voltage value of the filament current, comparing the collected data with data of the initial characteristic curve, wherein if an error is smaller than an error threshold value, then the equation of the section of the straight line is constant, and if the error is larger than the error threshold value, the collected data is utilized to renew the equation of the section of the straight line; using the equation of the straight line to calibrate the initial characteristic curve, selecting a corresponding equation of the straight line according to the pipe current value which needs to be utilized, and using the equation of the straight line to calculate the corresponding voltage value of the filament current. Through the calibration method of the X-ray generator tube current, calibration can be conducted on the pipe current of a ball pipe, and thus precise output of the pipe current is achieved.