1. An optimization method for relational structure, comprising: a) a zone controller receiving relational structure information, wherein the relational structure information comprises a relational structure composed of the zone controller and multiple groups of sub-relational structures; b) retrieving multiple groups of sub-relational structure information from the relational structure information by the zone controller; c) classifying the multiple groups of sub-relational structure information to generate a classified result by the zone controller, wherein the multiple groups of sub-relational structure information separately correspond to types, number and connection relation among multiple equipment controllers and sensors of corresponding sub-relational structure; d) separately executing an optimized searching procedure for each type of the sub-relational structure according to the classified result by the zone controller, and the executed optimized searching procedure comprises following steps: d1) searching multiple equipment controllers of same type located nearby according to the type of the sub-relational structure information by the zone controller; d2) respectively calculating a first relation level to each of the equipment controllers by the zone controller; d3) transmitting the sub-relational structure information to the equipment controllers by the zone controller; d4) respectively searching multiple sensors of the same type located nearby according to the received sub-relational structure information by each of the equipment controllers; d5) respectively calculating a second relation level to each of the sensors by each of the equipment controllers; d6) calculating a statistic value of the first relation level and each of the second relation levels by each of the equipment controllers respectively; d7) keeping a solution of a highest statistic value for matching the content of the sub-relational structure information as an optimized search result, and replying to the zone controller with the optimized search result by each of the equipment controllers respectively; e) separately retrieving the optimized search result for each type of the sub-relational structures by the zone controller; f) respectively establishing the sub-relational structure of each type according to the optimized search result by the zone controller; and g) connecting the sub-relational structures to establish the relational structure by the zone controller.