A method for controlling filament current of a computed tomography (CT) tube includes: detecting a present tube current of the CT tube and assigning the present tube current to a feedback value, calculating a difference between a set value of the tube current and the feedback value and assigning the difference to an error value, assigning a target upper bound value to a present filament current when the error value is greater than an first error threshold, and assigning a target lower bound value to the present filament current when the error value is less than a second error threshold, wherein the target upper bound value is greater than the target lower bound value, the first error threshold is greater than 0, and the second error threshold is less than 0.
