Disclosed are an anonymous communication system and a transmission method of an information transmission unit in the anonymous system. The method includes: after receiving an information transmission unit sent by a sending party, storing the information transmission unit in a storage pool, inserting the information transmission unit into a preset ordering queue, and generating more than one piece of index information according to content of the information transmission unit and information of the sending party; setting more than one index matching information of a receiving party; according to the index matching information of the receiving party, inquiring index information of the storage pool, finding out an information transmission unit set which meets the index matching information, selecting one information transmission unit from the set according to an ordering situation of each information transmission unit in the set in the ordering queue and a preset delivery strategy, delivering the information transmission unit to the receiving party, and adjusting the ordering queue according to a delivery situation. By means of the present disclosure, the degree of association between the receiving party and the content of the information transmission unit as well as the sending party can be improved, and the user response rate and activity can be improved.