Effect of long-term application of chemical fertilizers on content of organic carbon (SOC) in paddy soil was analyzed with the meta-analysis method. Results show that the practice increased SOC content in the top soil layer of the paddy field by 1.00 ± 0.23 g kg^-1, or by 1.06 ± 1.01 times as compared with control (CK). Analysis reveals that fertilization increased root biomass of the crop and hence input of carbon, and relatively sufficient nutrient supply from chemical fertilizer led to higher soil carbon sequestration efficiency. These two are believed to be the causes of higher SOC content in paddy field under long-term chemical fertilization. However, the effect of chemical fertilization varied with the rotation system. It was not so significant under the rotation system of rice-rice-upland crop, but was under the systems of rice-upland crop and rice-rice. One-way ANOVA analysis shows that in paddy fields, the same in fertilization, SOC content was the highest in the field under the system of rice-rice-upland crop, and little difference in SOC content was found between the other two rotation systems. Although application of chemical fertilizer significantly increases SOC content, it is essential to take into account comprehensively the emissions of greenhouse gases from the processes of manufacturing and transporting chemical fertilizers, besides the contribution of fertilization to global warming.