In order to prolong the life of the working gas in rare-gas halide excimer lasers, the real-time supply technology was added. This technology used FPGA control system to combine some operations effectively, such as improving the discharge voltage gradually, adding halogen gas and replacing part of the mixed gas. With the decrease of pulse laser energy, the discharge voltage was improved gradually. When the discharge voltage reached maximizing, it was time to add halogen gas and restore the discharge voltage. When the effect adding halogen gas was not apparent, part of the mixed working gas should be replaced. The technology was applied in medical ArF excimer laser, the experimental results show that the laser output energy of the laser drops by 17.2% after working 14.38 h accumulated without the real-time supply technology of working gas. But with this technology, the laser output energy decline rate is significantly lower, and it is stabilized successfully within the range of 3% working the same hours. Therefore, using this technology can extend the life of the working gas laser, increase the laser output energy stability, reduce downtime and lower operating costs.