This paper deals with the effect of organic material application on the chemical and thermal properties of HAs from brown soil, meadow soil and paddy soil in the field and incubation experiments. The results obtained are summarized as follows: In the field experiment, the number-average molecular weight(Mn) of HAs were markedly decreased by applying organic materials. For example, the Mn of HAs of CK, 18.7 (O₁) and 37.4 T/ha (O₂) of pig manure (PM) in brown soil were 1332, 835 and 578 zespectively. The same changes were found in other soils. PM was more effective than corn stalk (CS) in decreasing Mn of HAs in the incubation experiment. With the increase of the rate of organic materials applied. Mn of HAs decreased greatly. The Mn of HA in the incubated soil without application of organic material went up to 1768.