With the development of the red claw crayfish (Cherax quadricarinatus) aquaculture industry, Temnocephalans attached to the body surface of red claw crayfish and their hazards have attracted the attention of the industry. In this paper, the taxonomic status and distribution of Temnocephalans were summarized based on literatures. Then, their external morphology and internal structures were presented in detail. Additionally, their biological characteristics of symbiosis, feeding habits, life history and movement mode were described, and their harm to crayfish and their control measures were discussed. This review is considered to provide a reference for the red claw crayfish aquaculture, and to understand temnocephalans, their prevention and control.