A 90-day indoor incubation experiment was conducted to investigate the response ofzinc(Zn)availability and form transformation in purple tidal mud soil of calcareous paddy soil to different amountsof Chinese Milk Vetchadded.The results showed that the conversion of mineralresidual Zn(Min -Zn)and manganeseoxide bound Zn(OxMn -Zn)，which were difficult to be absorbed and utilizedby plants，as well as potentially effective carbonateboundZn(Carb -Zn)，toloosely bound organicZn(Wbo -Zn)and exchangeableZn(Ex -Zn)that wereeasily absorbed and utilized byplants，werepromoted.Thereby improving the bioavailability of Zn in purple tidal mudsoil.The average conversion ratio of Zn of purple tidal mud soil was the lowest in T1 treatment and the highest in T2 treatmentthroughout the entire studyperiod.By the endof the experiment，the Zn transfer factor of purple tidal mud soil was increased and the Zn allocation index of purple tidal mud soil wasdecreased with the addition of Chinese MilkVetch，which indicating that the Zn of purple tidal mud soil had transformed into aneffective component.There were differences in the effectiveness and morphological transformation of Zn in purple tidal mud soil with different amountsof Chinese Milk Vetchadded.The optimal addition amount of Chinese Milk Vetch was 22500 kg/hm².The research results could provide scientific basis for improving the effectiveness of Zn in purple tidal mud soil by planting Chinese Milk Vetch as green manure.