In this paper， the progress of the mechanism of milk fat crystallization is reviewed， and the effects of milk fat chemical composition， kinetic properties， fractal properties of polymorphic crystallization， and fat crystal networks are described in detail. In milk fat， the chemical composition of triglycerides plays a decisive role in fat crystallization. The melting point increased with the increase of carbon chain length when carbon chain is the same， the melting point order is： saturated fatty acid> conjugated trienoic acid> monoacrylic acid> diacrylic acid> nonconjugated trienoic acid. The melting point of α crystals is low， poor stability and hard to form. The melting point of β crystals is high， more stable and easy to form. The β′ crystals are optimum， which have good plasticity and taste. It is known from the fractal theory that the partial and whole structure of the system is similar in terms of morphology， function， and information. Through the microscopic analysis of crystal network， the overall structural performance can be deduced. In summary， fat crystallization plays an important role in dairy science. How to control fat crystallization to improve the quality of dairy products is of great significance.