Soil organic carbon content is an important index reflecting soil fertility，and the addition of organic materials plays an important role in improving soil organic carbon content. However，the systematic effect of organic material addition on soil organic carbon content under different natural conditions and agronomic practices is still unclear. By using the data collected from published literatures，a data set with the same soil organic carbon fractionation method from independent research was built up. Meta-analysis method was used to quantify the effect degree of applying organic materials on soil organic carbon content，and then the effects of natural factors and human factors on soil organic carbon content were quantitatively analyzed. The result showed that，compared with no fertilizer treatment，organic materials application significantly increased soil organic carbon content by 41.9%. The effects of applying organic materials on soil organic carbon content under different experiment region，soil texture，soil pH，initial soil organic carbon content，organic materials type，experiment duration and planting system were significantly different. The increase rate of soil organic carbon in North China(58.3%)was the highest and significantly higher than that in Northeast China(31.5%)and Northwest China(32.1%). The increase rate of organic carbon in clay and loam soil(48.2% and 41.7%)was significantly higher than that in sandy soil(25.0%)，and that in acid soil(29.4%)was significantly lower than that in alkaline soil(50.9%). The increase rate of soil organic carbon content(90.3%)with low initial soil organic carbon content(<6 g/kg)was significantly higher than those(37.7% and 38.2%)with high initial soil organic carbon content(6-12 g/kg and > 12 g/kg). The increase rate of soil organic carbon(87.8%)was significantly higher when the cumulative carbon inpute was >100 Mg/hm² than those(15.6% and 36.7%)when the cumulative carbon input was <50 and 50-100 Mg/hm². The increase rate of soil organic carbon by applying manure(46.5%)was significantly higher than that by applying straw(33.6%). The increase rate of soil organic carbon content(16.6%)in short time(<10 years)was significantly lower than that(47.0% and 52.2%)in long time(10-20 years and >20 years). The increase rate of soil organic carbon(47.8%)was significantly higher in double cropping system than that(32.4%)in single cropping system. Application of organic materials is of great significance to increase soil organic carbon content. From these results we concluded that to improve soil organic carbon content，soil characteristics of different regions should be considered. The most important measures to improve soil organic carbon content are to increase the amounts of organic materials per season，adhere to long-term application of organic materials and combine straw returning with manure application.