Abstract: To increase the activity of nicotinic acid hydroxylase of Pseudomonas sp.BK-1,the culture conditions of the strain were optimized.The experimental results show that 10 g·L^-1 sucrose is the optimal carbon source and 20 g·L^-1 corn steep liquor is the optimal nitrogen source.The optimized concentration of the inducer nicotinic acid is 12.5 g·L^-1 and initial pH of culture medium is 7.0.Under the conditions of rotation 400 r/min and ventilate 4.2 L/min the highest enzyme activity of this strain can reach 1.47 U·mL^-1 at 16 h in a 5 liter fermentor.The accumulation of 6-hydroxynicotinic acid in reaction mixture by Pseudomonas sp.BK-1 can reach 154 g·L^-1 at 36 h.