The present invention provides a method for multiplying current of an LED light bar, which includes (1) providing a constant current driving chip that includes driving modules each having first to three pins and resistors; (2) providing an LED light bar, a power source, and a PWM control source; (3) connecting an end of one resistor to the third pin of one driving module and an opposite end grounded, connecting the first pin of the driving module to the negative terminal of the light bar, connecting the second pin of the driving module to the PWM control source, and connecting the positive terminal of the light bar to the power source; (4) repeating step (3) as necessary to have multiple driving modules electrically connected to the light bar; (5) activating the power source and the PWM control source to allow the driving modules to simultaneous drive the light bar.