The invention provides a manufacturing method of a low temperature polysilicon thin film transistor, including: providing a substrate; forming a buffer layer on the substrate; simultaneously forming a polysilicon layer and a photoresist layer on the buffer layer; implanting ions into a source region and a drain region; removing the photoresist layer; forming an insulating layer on the polysilicon layer; forming a gate electrode on the insulating layer; and forming a passivation layer on the insulating layer. The passivation layer covers the gate electrode. The invention can only use one time of mask process and one time of ion implantation process to complete the manufacturing processing of the polysilicon layer, the manufacturing process can be simplified and therefore the cost of process is reduced and the productivity is improved.