Martensite is a common metallographic structure. Accurately revealing the objective law of the martensite transformation process is of great significance for controlling material organization and design materials. Herein, based on the phase‐field method, a 3D three‐variant martensite transformation model from the metastable to steady state is established based on the Khachaturyan. A. G. dislocation dynamic model. The transformation mechanism of martensite is analyzed and the transformation law and the law of growth behavior of variants is obtained. The research reveals the growth mechanism of martensite in multivariant martensite transformation, verifies the microstructure of steel after the quenching process, and proposes the “phagocytic” behavior of martensite transformation process and the prediction method of transforming variants. Finally, an interpretation of the interface fluctuations and residual austenite appearing during the transformation process is made. Herein, the objective law of martensite transformation is revealed, the universal prediction of martensite transformation morphology is realized, and an important theoretical basis for quenching tissue regulation and large‐scale high‐precision phase‐transition simulation is provided.