A lamp current control device includes an electronic power switch, a transformer, a current transformer and a pulse width modulation (PWM) IC. The transformer has its primary side connected to the electronic power switch and a secondary side connected to a lamp. The current transformer is serially connected with the primary side of the transformer. The PWM IC is coupled between a secondary side of the current transformer and the electronic power switch and uses the current transformer to feedback a feed back signal from the primary side of the transformer. The PWM IC receives and processes the feed back signal to obtain a control signal, and then the PWM IC outputs the control signal to the electronic power switch to control a pulse width outputted by the electronic power switch, thereby controlling and maintaining a brightness of the lamp.