This study aimed to enhance hyaluronic acid (HA) production of Streptococcus zooepidemicus by a two-stage dissolved oxygen (DO) control strategy based on the characterization of broth rheology and oxygen mass transfer.Culture broth was a kind of Newtonian fluid during 0-8 h and then exhibited a typical non-Newtonian characteristics afterwards with increased HA concentration.Oxygen mass transfer coefficient decreased with increased HA concentration.DO level decreased to nearly zero at 8 h and became a limiting factor for HA overproduction.Lactic acid production decreased while acetic acid production increased with increased DO level.