MLX1034 is from Polaribacter sp. Q13, and has the amino acid sequence of the 1,3/1,4-xylanase MLX1034 is listed in SEQ ID NO.1; a nucleotide sequence of the gene is listed in SEQ ID NO.2; the 1,3/1,4-xylanase MLX1034 in the invention is capable of efficiently and specifically degrading 1,3/1,4-xylan and producing xylooligosaccharides with DP values above one; in addition, the physical and chemical properties of the 1,3/1,4-xylanase MLX1034 are stable enough to hydrolyze 1,3/1,4-xylan at room temperature; the 1,3/1,4-xylanase MLX1034 is suitable for the industrial production of red algal xylooligosaccharides at low energy costs.