To study the fertility characteristics of paddy soil profiles at different fertility levels in typical northeastern counties，clarify the characteristics of high-fertility soils and the key obstacles factors of medium and low-fertility soil in typical northeastern counties，and provide a scientific basis for further improving paddy field fertility and rice yield in this region.Soil samples from 9 soil profiles with different fertilities were collected in paddy fields in 7 townships of Fangzheng County，Heilongjiang province.The thickness，soil bulk density，pH，organic matter，total nitrogen，total phosphorus，total potassium，alkali-hydrolyzed nitrogen，available phosphorus，available potassium，S2-，Mn2+，cation exchange capacity (CEC)，aggregate composition，microbial biomass carbon/nitrogen，and other indicators of the topsoil and plow layer soil were determined.Comprehensive soil fertility evaluation and stepwise regression analysis between rice yield and soil fertility indicators were carried out to explore the main controlling factors of fertility differences.The result showed that the contents of soil organic matter，total nitrogen，total phosphorus，alkali-hydrolyzed nitrogen，available phosphorus，available potassium，CEC，and Mn2+ in soil profiles with different fertility decreased gradually with the increase of soil depth，and all showed the order of high-fertility soils > medium-high-fertility soils > low-fertility soils.The high-fertility soils(the yield greater than 10000 kg/hm²)in Fangzheng county have a thick tillage layer，low bulk density，rich organic matter content，high total nitrogen content，medium total phosphorus content，and high organic matter，total nitrogen，and alkali-hydrolyzed nitrogen content in the tillage layer.The tillage layer of medium-fertility soils(the yield between 7500 and 10000 kg/hm²)has high organic matter content，medium total nitrogen content and low total phosphorus content.The low-fertility soils(the yield between 5500 and 7500 kg/hm²)have thin tillage layers，high soil S2- content，and other nutrient contents are lower than those of high-fertility soils.Available phosphorus and available potassium nutrients in high，medium and low-fertility soils reached abundant levels.There were significant differences in organic matter，total nitrogen，alkali-hydrolyzed nitrogen，microbial biomass carbon，0.25～0.053 mm aggregate content and manganese ion between high-fertility soils and low-fertility soils.There were no significant differences in most indexes except total phosphorus and cation exchange capacity between medium-fertility soils and low-fertility soils.The comprehensive soil fertility index of the tillage layer(14～20.7 cm)and plough layer(12.7～26.3 cm)of high，medium and low fertility soils were 0.70 and 0.83，0.42 and 0.49，0.21 and 0.26，respectively.The results of stepwise regression analysis showed that organic carbon and total phosphorus had the greatest effect on rice yield，while microbial biomass nitrogen and pH of tillage layer，available phosphorus and total potassium of plough layer had little effect on rice yield.The supply of organic carbon and total phosphorus nutrients in medium and low fertility soils was insufficient，and the contents of total nitrogen and alkali-hydrolyzed nitrogen were medium，and the tillage layer was thin in low-fertility soils.Therefore，it was suggested to apply organic fertilizer and phosphate fertilizer to medium and low fertility soils，and strengthen the management of fertilizer improvement and cultivation in order to achieve the yield target of high fertility soils.