A polarizer, a manufacturing method thereof and a display device are provided. The method includes forming an alignment layer on a carrier substrate and forming grooves on the alignment layer; providing liquid metal in the grooves, in which the liquid metal includes a plurality of liquid metal structures; applying an electric field parallel to the lengthwise direction x of the groove to the liquid metal to allow each liquid metal structure to be stretched along the lengthwise direction x of the groove to form a rod-like structure and the major-axis direction of each liquid metal structure is parallel to the lengthwise direction x of the groove; obtaining the liquid metal by curing the liquid metal; and stripping off the polarizer from the carrier substrate.