Abstract: This article studies the spatial distribution of organic matter at different depths in the plain areas of Yi'an, Fuyu, Baiquan, Keshan, Kedong, Nehe, Longjiang, and Gannan in the Qiqihar region of Heilongjiang Province, based on the test results of the black soil surface matrix survey in the Songnen Plain. Through Geographically Weighted Regression (GWR), shallow (0-20cm), middle (20-100cm), and deep (100-200cm) soil organic matter models in the Qiqihar region are constructed to further investigate the different factors affecting organic matter content. Through analysis, it was found that the organic matter content predicted by the GWR model at different depths is basically consistent with the measured organic matter content, showing a characteristic of high in the northeast and low in the southwest. The simulated GWR content of organic matter in shallow soil ranges from 1.12 to 80.7g/kg, with an average value of 26.50g/kg. The measured value ranges from 2.04 to 72.50g/kg, with an average value of 27.75g/kg; The simulated GWR content of organic matter in the middle soil ranges from 0.16 to 54.5g/kg, with an average value of 10.07g/kg. The measured value ranges from 0.00109 to 53.9g/kg, with an average value of 10.05g/kg; The organic matter content in deep soil ranges from 0.087 to 37.45g/kg, with an average value of 6.48g/kg. The measured value ranges from 0 to 38.26g/kg, with an average value of 6.47g/kg. The research results indicate that soil physical and chemical properties such as K₂O, Se, total phosphorus, and total nitrogen, as well as environmental factors such as annual average temperature, annual average rainfall, and altitude, all have varying degrees of impact on soil organic matter at different depths.