The strain of hyaluronan-producing bacteria that was Streptococcus thermophilus was used to study the hyaluronan production. We used the Plackett-Burman design of optimum multifactorial experiments to estimate the level effects of different factors such as peptone, meat extract, yeast extract, glucose, tween 80, K2HPO4, sodium acetate, ammonium citrate, magnesium sulphate and manganese sulphate on hyaluronan production. As a result, pepton (0.2%), meat extract (0.2%), manganese sulphate (0.0001%), temperature (40oC), K2HPO4 (0.04%), yeast extract (0.1%), glucose (0.4%), under which the hyaluronan production in Streptococcus thermophilus was obtained. The predicted maximum yied of hyaluronan in Streptococcus thermophilus was 86 mg/l.