Since the dynamic task allocation problem has gradually become one of the key points in the research of multi-agent systems (MASs), a booming development of agent cooperation methods reaches a point of warranting a survey. This paper firstly introduces the dynamic task problem and gives some analysis on multi-agent cooperation. Then, we introduce some popular multi-agent cooperation algorithms for dynamic task allocation in MASs, the cooperation rules on this issue. Also, this paper reviews the cooperation goals in literature. Finally, we give our analysis on benefits and future challenges in multi-agent cooperation.