1. A current modulation method in a computed tomography imaging system, comprising: selecting a plurality of discrete data points from an expected current modulation curve as approach points; establishing an actual current modulation curve, wherein an actual current value of the actual current modulation curve at an approach point approximates an expected current value of an expected current modulation curve, and a variation rate of the actual current is within an allowed range of the computed tomography imaging system; and modulating a current in an X-ray tube of the computed tomography imaging system according to the actual current modulation curve.