An electric rotary starter for an engine of a radio control model includes a motor mounted therein. A drive shaft is electrified and longitudinally connected to the motor and rotated by the motor. A conduct tube is electrified and movably sleeved on the drive shaft, wherein the conduct tube is insulated from the drive shaft. When starting the engine, the drive shaft is longitudinally inserted into the engine for providing torsion. Simultaneously, the conduct tube is longitudinally moved relative to the drive shaft to make the front end of the conduct tube contract with the engine. The conduct tube and the drive shaft from a circuit and the power from the electric rotary starter is transmitted to the spark plug in the engine to make the spark plug sparkle for starting engine.