The Ultraviolet Visible spectroscopic characteristics of soil dissolved organic carbon(DOC)in Central Gansu dryland soil in 2022 and 2023 were investigated in a field trial conducted in Lijiabu township，Dingxi city，Gansu province in 2021 using Ultraviolet Visible spectroscopy. Five treatments were set up，including single application of biochar(B)，returning straw to the field(S)，combined application of biochar and straw(BS)，one-time addition of 4-year biochar(B4)，conventional fertilization(CK). The results showed that the addition of straw and biomass charcoal significantly increased the DOC content，and the DOC content was higher in the S treatment，which was 141.90%-223.79% higher than that in the CK treatment. Both straw and biomass charcoal addition treatments significantly increased the content of coloured dissolved organic matter [characterized by α(355)]，and the B treatment was the most effective，with a significant increase of 191.22%-244.10% compared to the CK treatment. The spectral absorption value SUVA254，SUVA260 and SUVA280 of DOC increased with the addition of straw and biomass charcoal，but the effect of S treatment was not significant；the addition of organic materials decreased spectral absorption ratio E2/E3，E3/E4，E4/E6，and the decreasing trend was most significant in S treatment. The E3/E4 values of DOC in the 10-30 cm soil layer of the CK treatment and the B，S，BS and B4 treatments were all greater than 3.5，indicating that the soil DOC was mainly dominated by fulvic acid，while the E3/E4 values of DOC in the 0-10 cm soil layer of the B，S，BS and B4 treatments were less than 3.5，indicating that their soil DOC was mainly dominated by humic acid. In summary，the S treatment had the best effect on the improvement of DOC content and humification，and the BS treatment had the best effect on the improvement of aromaticity，hydrophobicity and molecular weight of DOC molecules.