There exist several problems in the maintenance of phased array antenna, such as high maintenance costs, unsure maintenance chance, complicated model simulation and arithmetical operation. Considering these problems, a maintenance optimal model was put forth on the basis of regional quantification. A regional quantification model was given, and then the maintenance problems of phased array antenna were turned into the maintenance optimal of a k/n system, which consists of different regional array elements. A maintenance optimal model for the antenna was built, which chooses minimum maintenance costs per unit time as the object and the operational availability as the subject. Simulations and analysis of one instance were conducted to verify the validity of the proposed model. The results show that the proposed model could solve the maintenance problems of the asymmetrical array antenna well. 