To release and solve traffic jam on expressway, it is necessary to investigate the ramp metering strategy of expressway. Current specification and field data were used to build the VISSIM simulation model. The breakdown probability models of expressway ramp were established by microscopic traffic simulation, and a ramp metering strategy based on breakdown probability model was put forward. According to the mainstream and ramp volume, the breakdown probability was predicted. If the probability is higher than the threshold, the metering system turns on, and the on-ramp metering rate and cycle time are calculated. Compared with a ramp without metering strategy, the breakdown probability reduced to about 0.1, while the speed of mainstream increased by about 20 %.