This study considers design of reliability acceptance sampling plan (RASP) for failure rate qualification at selected confidence level. The lifetime distribution of product is assumed to be exponential. MIL - STD - 690 C and KS C 6032 standards provide this procedure. These standard offer acceptance number and total testing time to decide failure rate level of product. But selection method of acceptance number is not presenting. Average outgoing failure rate (AOFR) which is long-term average of failure rate of accepted product is very important in side of reliability assurance of products. Formula for computing AOFR is derived and a method of design a RASP which satisfies AOFR`s limit requirement is proposed. Additionally, a selection method of acceptance number considering total testing cost and reliability assurance cost at the same time is also suggested.