The article introduces an analysis and design of simmer circuit for lasers.The application of simmer circuit can improve efficiency of converting electricity to light,adopting the way of both high voltage and low voltage to provide power,which is almost constant current source.The status of stable discharge is offered by the high voltage part,while the sustaining current indispensable for proper work of lamp is supplied by the low voltage part.The cooperation of high voltage and low voltage can strengthen efficiency of simmer circuit.