Bio-humic acid is a new non-coal humic acidresource，which was obtained from cropstraw，wood chips， bagasse and other agricultural wastes by chemical or microbial fermentation process. It is an important resource of green fertilizer and an important way to solve the comprehensive utilization of agricultural wastes. Bio-chemical fulvic acid(FA)and bio-chemical potassiumhumate(HA -K)were prepared and extracted after nitrification and alkali extraction with rice straw(RS)as raw material and HNO3 as oxidant in this study. The structural changes of RS before and after extraction were studied by three major components’contentsanalysis，thermogravimetric analysis and soild carbon nuclear magetic resonance(13CNMR)analysis. Results showed that after nitrification and alkaliextraction，the proportion of cellulose in the residue(ER)reached as high as 91.26%-96.78%. The main weight loss temperature was concentrated at350-420℃，which belonged to cellulosecracking range，accounting for 75.49%. In the 13C NMR spectrogram of ER-10% 60min，the carboxyl and carbonylcarbon(N°1)contributed by the carbonyl group in the acetoxy group of lignin and the carboxyl group in hemicelluloseand the aromaticcarbon(N° 2 -6) contributed by the aromatic structure of lignin disappeared. These phenomena reflected that the hydrogen bond and ester bond connecting the three major components were broken during nitrification and extraction. Thecarbonyl and carboxyl functionalgroups(N°1)in lignin and hemicellulose and the aromaticstructure(N° 2 -6)in lignin entered FA and HA-K，and cellulose was left as the main component in ER.