The present invention discloses an aspergillus niger 6-4 photolyase and a constructing method thereof. The aspergillus niger 6-4 photolyase has a nucleotide sequence of SEQ ID NO.1. The constructing method is as follows: a 6-4 photolyase gene An6-4 is obtained from existing wild type aspergillus niger, a nucleotide sequence is redesigned, codons preferred by an escherichia coli expression system are optimized to obtain a modified gene An6-4', and a gene fragment is ligated with pET22b plasmids to construct recombinant expression plasmids; and the recombinant plasmids are transformed into escherichia coli competent cells to construct genetically engineered bacteria, and the genetically engineered bacteria obtain a relatively good expression at 20 DEG C and 1 mM IPTG. Compared with the priorart, the 6-4 photolyase is successfully expressed in a heterologous expression system, active soluble proteins are to obtained, and the aspergillus niger 6-4 photolyase has extremely excellent anti-oxidation ability, is long-lasting and stable in activity, and can applied in the fields of biomedicines and cosmetics.