The analysis results of 110 loess samples from the middle reaches of the Huanghe River show that the contents of Organic matter range from 0.179 to 0.883%,with an average value of 0.390%,most in extent of 0.2000.600%.The contents increase from northwest to southeast.The contents of the organic matter in loess profile decrease with depth increasing.The phenomenon known as"been lost"of organic matter are observed in both loess and paleosol,This process might be accomplished 800,000 years ago,