Computer Aided Urban Planning System(CAUPS)is an object and agent based computer aided urban planning system that uses the entity agents as its basic units during the process of urban planning.The evaluation factors of multiple entity agents system,i.e.the communication mode and attribute adjustment strategies of multiple entity agents,are analyzed,then a KQML based multiple agents communication mode is introduced.Based on this communication mode,the attribute adjustment function between multiple entity agents is realized.The reciprocity relationships of agents in CAUPS are divided into three basic types,i.e.single entity agents attribute adjustment, dual entity agents attribute adjustment and transitive entity agents attribute adjustment.Finally, the weak synchronization algorithm is presented to solve the problems of the single entity agents attribute adjustment and the dual entity agents attribute adjustment.And the strong synchronization algorithm is proposed to deal with the transitive entity agents attribute adjustment.