The invention discloses an N-acetyl homoserine lactonase-xylanase fusion protein and a coding gene and application thereof. The protein is (a) or (b) shown as follows: (a) refers to a protein with an amino acid sequence shown as a sequence 1 in a sequence table; (b) refers to a protein which is derived from the sequence 1 by carrying out substitution and/or deficiency and/or addition with one or more than one amino acid residue on the amino acid sequence of the sequence 1 and has the same function with the protein shown as the sequence 1. In the invention, an N- acetyl homoserine lactonase gene with quenching enzymatic activity and a xylanase gene are fused to obtain the fusion protein (N-acetyl homoserine lactonase-xylanase fusion protein) SL2B-6. The fusion protein has suitable action pH value, stronger metal ion and surface active agent resistance, stronger protease resistance and better capacity of hydrolyzing various substrates and can be used as a novel feed or food additive applied to feed and food industry.