At present, there is a very important and valuable data that has been neglected in the surging tide of big data research, which is the “Third Data” proposed in this paper. The Third Data is the data with subjective characteristics generated by problem handlers in the process of problem handling. The Third Data contains the empirical knowledge of problem handling with a great density, and is an indispensable knowledge resource for problem definition, problem analysis and problem solving. This paper defines the concept of the Third Data, and discusses the characteristics and sources of the Third Data. The generating process of the Third Data is analyzed through “practiceexperiencedata” and a fivestar spiral model of Third Data is proposed. Actual case analysis shows that the exploitation and utilization of Third Data have significant value in reducing the cost and improving the benefit. This paper also puts forward ten topics related to the indepth study of Third Data. The Third Data has the inherent property of transforming the world, as well as a problemdriven universality. Each aspect contains a problem related to Third Data in some way. Therefore, the theoretical results of Third Data have a more general and universal meaning, applicable not only to manufacturing industry but also to services, even in the social and economic fields.