The problem of dynamic risk essentially belongs to the problem of risk perception and one of its methodologies is based on risk field. By introducing morphogenetic system theory, aiming at exploring the developmental mechanism of the risk system, a method to understand risk field based on its morphogenesis was discussed in detail. Firstly, the problem of risk field essentially belongs to the problem of risk measurement and risk expression and risk field is a kind of morphic field, which is the reason of morphogenesis of risk system. Secondly, it discussed the relationship between risk and form and pointed out that risk is an non-living form. Thirdly, the morphogenesis of probabilistic risk was given and the framework of the construction project risk field research was proposed in details. At last, morphogenetic estimation, which is based on the morphogenesis of data, can be used to estimate the relations in risk analysis. This research can improve the theory of risk analysis of construction project and contribute to exploring the developmental mechanism of the risk system based on the form.