Yaks (Bos grunniens) are the most economically important mammals on the Xizang Plateau, pro- viding milk, meat and income for people.Calcium as Ca2+ controls the maturation process of oocytes, maintains fertilisation and initiates embryonic development.The activator as Ca2+ at 0.20, 0.22 and 0.24 mM and the inhibitor KN-93 at 0.5, 1.0 and 1.5 lM were added to compare maturation rate of oocytes in vitro.Immunofluorescence staining analyzed the antioxidant levels of reactive oxygen species (ROS) and glutathione (GSH) and the expression of CaMKII in the mature oocytes.The growth related genes c-fos, epidermal growth factors EGF and EGFR and apoptotic genes BAX, BCL-2, were detected in mature oocytes after 24 h of culture using a real-time quant. polymerase chain reaction.The oocyte maturation rate was the highest at 58.43 ± 3.37% when the culture temperature was 38.5degree C and 57.6% when the concentration of FBS was 15%, significantly higher than 55.6% at 10% and 53.8% at 20% (p < 0.05).The ROS level of mature oocytes reached the highest level in 1.5 lM KN-93 group, and the expression of BCL-2, EGF, EGFR and c-fos mRNA was increased by adding Ca2+.The KN-93 decreased the expression of BCL-2, EGF, EGFR and c-fos genes.The study showed that Ca2+ could regulate the levels of GSH and ROS by activating CaMKII, activity and it improved the maturation rate of oocytes in vitro.