In recent years, as a new method of environment sensing, data collecting and information providing, crowd sensing has gradually become one of the research highlights. Incentive mechanism is one of the most important research problems in crowd sensing. The method refers to certain mechanism design that encourages participants to join in sensing tasks and provide high-quality and reliable sensing data. This paper reviews the researches on incentive design of crowd sensing in recent years. First of all, crowd sensing and crowd sensing incentive design are introduced. Then, starting with key techniques, the main incentive methods and the core problems in incentive design are described. Finally, existing work, research challenges, and future directions are discussed. This work is to provide valuable reference for the related researchers.