| Summary: | The formation mechanisms of the precursor film (PF) at high temperature were reviewed, i.e., surface diffusion mechanism, evaporation-condensation mechanism, subcutaneous infiltration mechanism, and rapid absorption then film overflow mechanism. In the experimental metallic systems, the most possible mechanism is the subcutaneous infiltration mechanism, which is related to the apparent contact angle, contact radius, height of gap between the substrate metal and oxide film. In the metal/ceramic system, the formation of precursor film is usually rapid absorption then film overflow mechanism. The appearance of PF for adsorption mechanism needs to meet the contradiction of relative inertia and high affinity at the liquid/solid interface. Meanwhile, another possible mechanism of precursor film in high temperature reactive wetting system, namely film transport mechanism, is introduced. It was pointed out that the difficulty of studying precursor film lies in the unpredictability and instability of precursor film, and its development direction should be systematic, and the corresponding theoretical model should be established.
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