Light emitting diode(LED)is provided with the virtues of saving energy, environment protection , long lifetime and compact size, etc. It has been widely used in a lot of outdoor lighting applications as a new semiconductor light source. To solve the problems of the traditional single-stage and two-stage structures, an interleaved flyback converter is researched, which has simple structure and higher power level. And also a PFM control method is proposed, it changes the switching frequency and the turn-on time according to the different load conditions, reduces the switching loss in light load condition and improves the efficiency of the LED driver. Experiment results are presented to verify effectiveness of the theory analysis.