This book discusses some skills of playing mahjong from the perspective of mathematics and mathematical games. There are two purposes to do this: one is to correct the name of the mathematical toy mahjong; The second is to warn people who like to play mahjong. Playing mahjong can't be gambling, not by luck, but by "calculation". This requires knowledge of probability theory and good use of mathematical logic thinking. The content includes eight chapters: Mahjong terminology, Mahjong is a mathematical game, Mahjong permutation and combination mode, and matters needing attention in Mahjong game.