Abstract: The disclosure discloses a preparation method and application of a non-noble metal single atom catalyst, and belongs to the technical fields of chemistry, chemical engineering and material science. According to the disclosure, cheap raw materials and simple method are used to prepare the single atom catalyst. In essence, metal is anchored on light-absorbing carrier in a single atom form under irradiation to produce the single atom catalyst. In the disclosure, the non-noble metal single atom catalyst is prepared by using a photochemical synthetic route for the first time. The single atom catalyst synthesized in the disclosure is dispersed on the surface of photoactive substance. Using nickel single atom as a co-catalyst in photocatalytic water splitting to produce hydrogen, the cost is low and the catalytic efficiency is greatly improved compared with other types of non-noble metal modified composite photocatalysts.