Decomposition of organic materials in cropland soils is critical to recycling of soil carbon (C) and nutrients. We collected data from the 56 published studies during 1980—2013 that have examined the decomposition of organic materials across China. Our objectives were to to quantify the fraction of C remaining after one year’s decomposition (h₁) and to investigate the impact of types of organic materials (green manure, straw, root and manure) and agricultural regions (Northeast, Northwest, North and South China). Overall, h₁ ranged from 0.10 to 0.75 g g^-1, with an average of 0.335 ± 0.005 g g^-1 across China, and was significantly affected by types of organic materials and agricultural regions and their interactions. On the whole, in terms of h₁ the four major types of organic materials displayed an order of green manure < straw < root and organic manure, and the regions, an order of South China ≈ North China < Northwest China ≈ Northeast China. However, the regional variation of h₁ was also affected by type of organic materials. For instance, h₁ of straw, root and green manure were lower in North China than in South and Northeast China, whileh₁ of organic manure did not differ much between regions. On the other hand, h₁ of organic materials also varied with the regions. For example, in humid and semi-humid Northeast, North and South China, h₁ of root was higher than that of green manure and straw, while in the arid and semi-arid Northwest China, h₁ did not differ much between types of organic materials, because of aridity. Step-wise regression analyses shows that lignin:N ratio is the major factor regulating decomposition of straw, root and green manure, while mean annual temperature and aridity follows in the effect. However, decomposition of organic manure, which had already been decomposed or semi-decomposed, was not significantly affected by climatic factors, nor by quality (chemical composition) of the organic material. In addition, a singer factor, either of climate or of quality of organic materials, could maximally explain no more than 15% of the variability of h₁, and the combination of climatic factors and quality of the organic materials could only explain less than 40% of the variability, which suggests that to predict accurately the decomposition processes of organic materials in cropland, more attention should be paid to impacts of the regional or site-specific characteristics, such as soil physic-chemical and biological properties.