The invention belongs to the technical field of natural gas engines, and discloses a natural gas engine mixer which mainly solves the problem that an existing mixer can not mix natural gas with air very well. The natural gas engine mixer is mainly characterized in that a step is formed between a mixing zone of an air inlet duct and a mixer air outlet; the diameter of the mixer air outlet is less than that of the mixing zone; a first interior supporting piece in an annular structure and a second interior supporting piece in an annular structure are respectively fixed on the two sides of a natural gas inlet duct; an air outlet hole is formed between the first interior supporting piece and the second interior supporting piece; an annular vacuum region communicating with the natural gas inlet duct is formed by the first interior supporting piece and the second interior supporting piece; the first interior supporting piece is in a conical barrel shape; and an exhaust through hole is formed in a part, on the outer side of the first interior supporting piece, of the air inlet duct. The natural gas engine mixer has the characteristics that natural gas and air are subjected to secondary mixing, the mixing is more uniform, and the natural gas engine mixer is safe and efficient and exerts a protective effect.