A three-year (2016—2018) field trial was conducted at the Changchun Comprehensive Experiment Station of the Northeast Institute of Geography and Agroecology, Chinese Academy of Science, which is located in Changchun city, Jilin province, China. The purpose of this study was to investigate the effects of biochar (BR), straw (SR) and combination of biochar and straw (BS) on physicochemical properties and dissolved organic matter (DOM) characteristics of black soil. The results showed that the BR, SR and BS treatments significantly increased the maize yield and biomass, mean weight diameter of soil aggregates, and leucine amino peptidase activity compared with the control (CK). In addition, compared with the CK treatment, the BR treatment significantly reduced the humification index (HIX) by 10.0% and significantly increased the contents of KMnO₄-oxidizable carbon and available phosphorus by 35.6% and 51.3%, respectively. Meanwhile, compared with the CK treatment, the SR treatment significantly increased the maximum fluorescence intensity of emission wavelengths of 440~470 nm, when excitation wavelength was 355 nm (Fn (355)), HIX, the ratio of the absorbance at 254 nm to the dissolved organic carbon concentration (SUVA₂₅₄) and total nitrogen/total phosphorus by 43.6%, 4.1%, 45.5% and 18.8%, respectively. Moreover, the BS treatment significantly increased soil pH, organic carbon/total phosphorus, available potassium contents and the ratio of absorbance at 250 nm to absorbance at 365 nm (E2/E3) compared with the CK treatment. In general, biochar application could reduce the humification degree and complexity of DOM and improve the content of soil labile organic carbon, whereas straw return could enhance the humification degree and complexity of DOM.