Abstract: Both enzymic and nonezymic l ipid oxidation existed in the micr osomes insolated from muscle of gr ass carp .The experimental resul ts showed that Fe3+ or Fe2 ions wer e required for the enzymic lipid oxidation .The ra te of oxidation was highter with Fe2 than tha t wi th Fe3 ions .The opt imum pH for the react ion of both red and white muscle microsome was between 6 .0 and 7 .0 .The inter action of H2O2 with Hb to form activated MetHb was able to init iate nonenzymic catalysis oxidat ion of lipid in microsomal fract ions of both types of muscle .The stongest e ffect of per oxida tion was observed when the r atio of heme group to H2O2 was nearly 1∶1 .