This paper introduces a Runback(Referred to as RB)function test carried out on a W Flame boiler unit

which is equipped with the double-inlet and double-outlet coal milling system

heavy fuel oil guns and double cyclone burners. It focuses on the logic function design

preparation test and test attentions.The process of RB function test has been described

analysis of the RB test data shows that there are some problems in the test process

and the corresponding solutions and logic optimization were presented

after then the RB function can be successfully conducted in practice. The realization of RB function would improve the operation security coefficient as well as the economic and social benefits.