The culture conditions for the production of extracellular agarase by Pseudomonas aeruginosa ZSL-2 were optimized using One-Factor-At-A-Time combined with orthogonal array design. One-Factor-At-A-Time method investigates the effect of time, temperature, NaCl, carbon sources, nitrogen sources and pH on agarase production. The optimized culture conditions obtained from the statistical analysis were temperature of 30 °C, pH 8.5, NH4NO3 2 g L-1 and agar 3 g L-1. The L9 orthogonal array design was used to select the fermentation parameters influencing the yield of agarase. The order of the factors affecting the fermentation process was found to be NH4NO3 > pH > agar > temperature, with temperature playing a significant role on the agarase production (p < 0.10). The higher yields than those in basal media culture were obtained in the final optimized medium with activity of 0.439 ± 0.013 U ml-1. Extracellular agarase hydrolysed agar into a range of oligosaccharides which were analysed by LC-ESI-MS spectrometry as anhydrogalactose, galactose, agarobiose, agarotetrose and agarohexaose.