To higher biomass and antimicrobial activities of marine bacteria Paenibacillus polymyxa L1-9 in a 50 L fermenter,the technological processes were optimized with batch and fed-batch fermentation.The result showed that the best process for batch fermentation was following.Inoculum size was 8 % with culturing after 24 h and cell concentration was 109 cell/mL.Initial rotating speed and ventilator capacity were 250 r/min and 3 L/min respectively.The max biomass,2.40×1010 CFU/mL,was achieved after 11~12 h fermentation.For fed-batch process,the max biomass,4.63×1010 CFU/mL,was obtained after 30 h.This result was based on keeping 0.4g/ L reducing sugar in medium by adding 6g/L glucose after 13h growing.Comparing to batch fermentation,fed-batch fermentation yielded increasing 78.07% products.The antimicrobial activity of L1-9 to Staphlococcus aureaus was tested here.There was an ascending trend when the biomass increased.The activity reached its top at 20h when the inhibition zone was 17.75 mm.The conclusion is that there is a positive correlation between antimicrobial activity and biomass of L1-9 and it is a growth associated strain.