A 12-day experiment was conducted to compare the differences of Gracilaria blodgettii and Gracilaria bailinae from decay process.Results showed:(1) At end of experiment, G. blodgettii body weight lost 22.52% at 10 days while G.bailinae lost 8.5% at 8 days,stating they were at early decomposition process.The decomposition process presented two obvious phases,the decomposition rate of G. blodgettii was greater than G.bailinae.Furthermore, the physiological responses of algae were changing,G.blodgettii malonaldehyde (MDA) content showed higher than G.bailinae, but in contrast of the activity of superoxide dismutase (SOD),indicating that the memberane system of G.blodgettii suffered serious damage,and weakened in antioxidant capacity.(2) The percentage of nitrogen decomposed was higher than that of phosphrous,and the release of phosphorus lagged behind nitrogen.Besides, the order of nitrogen amount realeased from the algae was G.blodgettii and G.bailinae,the order of total phosphorus amount released was G.bailinae and G.blodgettii. But G.blodgettii total nitrogen and total phosphorus in the water was greater than that of G.bailinae.(3) G.blodgettii moisture content and C/N initial value was 95% and 52.11, G.bailinae moisture content and C/N initial value was 91% and 24.01,after which the values fell.In conclusion, G.blodgettii had a longer decay time, the higher algae body weightlessness rate and decomposition rate,besides, G.blodgettii antioxidant ability was weak,but total nitrogen released more. So G.blodgettii suffered more serious decomposition than G.bailinae. Therefore, we inferred that algae nitrogen and phosphrous concentration, the ability of antioxidant,algae moisture content and C/N ratio may be the factor which caused two gracilaria genera algae differences in early decomposition and nutrient releasing.