Soil organic matter (SOM), as an important source of various nutrient elements in soil, plays a very important role in promoting formation of soil structure, improving soil physical properties and increasing soil nutrient retention capacity. Therefore, based on the second provincial soil survey in 1982 and soil sampling in 2009, and soil classification in line with the soil taxonomy, the paper elaborated regulations of spatio-temporal variation of SOM content in various types of soils in Henan Province, one of the major grain producing provinces of China and analyzed major affecting factors of the variation, with the aid of the techniques of traditional statistics, geostatistics and GIS. Conclusioons of the paper may serve as guidance and reference in implementing rational fertilization and nutrient regulation in Henan Province. The data of 1982 were cited from the Second National Soil Survey. Soil sampling distribution maps of all the cities and counties of the province plotted in the survey were scanned and vectorized, and 1110 typical soil sampling sites were screened out. And the data of 2009 was collected from field sampling,,covering a total of 1615 soil sampling sites. The analysis shows that the mean content of SOM increased from 12.21 g kg^-1 in 1982 to 16.02 g kg^-1 in 2009, or by 31.20%, and its coefficient of variation decreased from 67.90% to 35.52%, which indicates that the SOM contents of the two periods were both at a medium level of variation. The variograms of SOM in the two years both fitted the spherical model, with nugget coefficient decreased from 56.10% to 60.18%, and codomain from 569.05 km to 547.22 km, suggesting that the effect of stochastic variability of SOM intensified and spatial autocorrelation weakened. Through referencing between Genetic Soil Classification of China (GSCC) and Chinese Soil Taxonomy (CST), the soils of Henan Province could preliminary be sorted into 6 orders, 12 suborders, 20 groups and 38 subgroups in accordance with the CST. A general trend was observed that the content of SOM was increasing from the west to the east and the increase was more significant in the plain areas, while the content of SOM of the mountainous regions in the west, north and south of the province somewhat decreased. Besides, from 1982 to 2009, the area of soils with SOM content ranging between 15.0 and 20.0 g kg^-1 increased from 37.3 thousand square kilometers to 123.5 thousand square kilometers, or by 51.60%, and SOM contents in the other areas level all decreased somewhat. The soils of Endorusti-Ustic Cambosols, Ochri-Aquic Cambosols, Irrigation-Orthic Anthrosols, Ustic-Alluvic Primosols, Ustic-Sandic Primosols, Hapli-Udic Vertosols and Hapli-Udic Cambosols in the soil taxonomy all increased by of 5.7, 6, 5.6, 5.5, 5.4, 5.0 and 3.1 g kg^-1, respectively, in SOM content While the soils of Ustic-Orthic Primosols and Hapli-Orthic Primosols declined by 2.5 and 1.9 g kg^-1. According to the conditions in Henan, the main factors that lead to sharp spatio-temporal variation of SOM between different soil groups are believed to be parent material, climate, soil texture, land use and human activity,or further in detail,,soil particle size and viscosity degree of parent material; temperature and humidity of climate; clay content in soil texture; forest cover and cropping system in land use and straw incorporation in human activity. The soil groups with increasing SOM content are mainly distributed in cultivated land of the plain, where incorporation of crop straw and application of organic manure increases SOM content in the soils.