A manufacturing method and apparatus of low temperature polycrystalline silicon, and a polycrystalline silicon are provided. The manufacturing method of low temperature polycrystalline silicon includes forming an amorphous silicon layer on a substrate; scanning the amorphous silicon layer by using a laser to emit a strip-shaped laser beam to go through a mask which includes transmissive stripes and partially-transmissive stripes arranged alternately, to form low temperature fusion regions and high temperature fusion regions which are arranged alternately on the amorphous silicon layer; recrystallizing the amorphous silicon layer from the low temperature fusion regions to the high temperature fusion regions.