The present invention relates to a kind of starter of liquid rocket engine and design method thereof, is provided with propellant storage tank, add discharge valve, solenoid valve, gas generator and igniter; Store nontoxic self-pressurized propellant in the propellant storage tank, because The saturated vapor pressure of the medium is relatively high, and the driving pressure of the propellant can be provided by using the pressure of the medium itself; there is a filling and discharging valve connected to the connecting pipeline between the storage tank and the solenoid valve to fill and discharge the non-toxic self-pressurized medium. After the solenoid valve Connect the inlet of the gas generator through the pipeline, ignite the propellant to generate gas, and the gas enters the downstream turbine casing at high speed, and drives the turbine to rotate to realize the start of the engine. The invention adopts the nitrous oxide-based composite propellant, which has the advantages of green and non-toxic, high saturated vapor pressure, high specific impulse, low use cost and easy maintenance. The starter is simple in structure, light in weight, non-toxic and pollution-free, can be started many times, and can be used repeatedly.