A method of manufacturing low temperature polysilicon is provided, comprising: depositing a buffer layer (20) on a base substrate (10); depositing an amorphous silicon layer (30) on the buffer layer; performing a heat treatment after forming the amorphous silicon layer; and dividing the amorphous silicon layer into a plurality of areas for laser annealing according to a thickness distribution of the amorphous silicon layer to form a polycrystalline silicon layer. A low temperature polysilicon film manufactured by the low temperature polysilicon manufacturing method and a thin film transistor having the film are also provided. The method realizes large grain size for polysilicons in each area of the amorphous silicon layer and a uniform distribution of polysilicon grain size across the entire substrate.