Abstract: For the existing electric ignition and flame detection systems in marine supercharged boiler are of no logic protection function and easily lead to incorrect manipulation,an improved design method based on PLC is pre sented.Based on PLC technology rather than conventional relay control loop,the system is consisted of five sub-loops as follows: normal ignition loop,emergency ignition loop,boiler chamber flame detection loop,boiler sandwich flame detection loop and alarm loop.The configuration design of PLC and the application of logic protection function are introduced.This improved method,implemented on the new type equipment,leads to less work demands of crewman and improvement of system security and reliability.