For the problem of the cracks which appear in batches in the fuel-oil accessories rear cover, a new evadable measure for the crack guide and devolvement is put forward, by researching the main cause of the cracks and analyzing the extent of the damage caused by the cracks in different positions in the fuel-oil accessories rear cover for the aero-engine, The method changed the pristine support construction, so the new stress concentration point was formed and the stress amplitude in the key part of the stress concentration area was reduced, which transferred the crack faults from the unrepaired key part to the repairable non-critical part. Through computer simulation, the optimal parameters for the crack guided gap were determined, and the simulation result showed that the evadable measure for crack guide and devolvement is reasonable and practicable.