After bearing ring forgings are forged, the dimension of finished forgings is needed to be measured at any time because of thermal deformation shrinkage in cooling process. However, there is a misjudgment on dimension in the process of thermal detection usually. In order to solve the problem of thermal detection misjudgment, three determination methods for thermal deformation shrinkage coefficient were studied by the principle of mathematical statistics and regression analysis method, and the deviation of the three methods were compared, then the "Temperature and dimension table on forgings" was figured out. Based on the table，the thermal detection on forging dimension was carried out to ensure that the cooled forgings can meet process requirements .