Auxiliary power unit (APU) fluid drainage certification test for civil aircraft is one of the most difficult issues during civil aircraft certification. As an aircraft integration test, it is involved with APU system design, aircraft general layout design, aerodynamic design, APU compartment and tailcone structure design, etc. The paper studies auxiliary power unit (APU) fluid drainage certification test , and the key technology points for relevant test methods, modification and instrumentation and the compliance criteria during ground and flight tests are obtained.