The present invention relates to the field of 3D display technology and provides a polarizer, manufacturing method thereof, and a 3D display device. According to the present invention, a transition layer is provided between an alignment layer and a supporting layer, and there is excellent wettability between the transition layer and the supporting layer as well as the alignment layer. The polarizer comprises a polarizing layer for producing linearly polarized light, a supporting layer located at one side of the polarizing layer, a transition layer arranged on one side of the supporting layer away from the polarizing layer, an alignment layer arranged on one side of the transition layer away from the polarizing layer, and an optical rotation layer arranged on one side of the alignment layer away from the polarizing layer.