Abstract: To study the inhibition of development of biofilm in Pseudomonas fluorescens FML05-2 by cinnamaldhyde at the non inhibitory concentration. Firstly, it was studied that the effect of the cinnamaldhyde on the purple pigment production by Chromobacterium violaceum CVO26 as model bacteria, then determined the biofilm formation and extracellular polysaccharide ( EPS) production that was important factors correlated with the biofilm formation in P. fluorescens FML05-2. The results indicated that the cinnamaldhyde inhibited the purple pigment production of C. violaceum CVO26, the inhibition rates were31.53% and 17.90%, respectively.The inhibition rates of the biofilm development were 44.22%, 21.77%, the inhibition rates of EPS production were 15.72%, 5.34% in P. fluorescens FML05-2 at the non inhibitory concentration of 40 μg/m L and20 μg/m L. The results suggest that the cinnamaldhyde can inhibit the development of biofilm in P.fluorescens FML05-2 at the non inhibitory concentration