Projection system and projection method

A projection system, comprising:

• a processing module;
• a projection module, coupled to the processing module, and configured to project a first projection image, wherein the first projection image comprises a first asymmetric graph;
• and
• a photographing module, coupled to the processing module, and configured to capture at least a part of the first projection image based on a photographing range, so as to output a first photographed image, wherein the first photographed image comprises at least one second asymmetric graph,
• wherein the processing module is configured to analyze the first photographed image to determine whether the at least one second asymmetric graph is consistent with a geometric configuration of the first asymmetric graph, and is configured to determine an effective photographing area by excluding areas in the first photographed image that are inconsistent with the first projection image, according to one of the at least one second asymmetric graph that is consistent with the geometric configuration of the first asymmetric graph in the first photographed image.