In order to study the effect of Schizochytrium feeding on the growth performance in yaks, 24 healthy male yaks aged 2-3 years were divided into control group and microalgae group, with 12 in each group. The control group was fed with basic diet, and the microalgae group added 200 g·head^-1 Schizochytrium to the basic diet every day for 60 days. During the experiment, the changes of daily average feed intake of yaks in two groups were recorded; The changes of body weight and body size were measured before and after feeding; Changes of serum Growth hormone (GH), Triiodothyronine (T3) and Thyroxine (T4) were detected and analyzed by ELISA. After feeding, the carcass percentage was calculated by separating organs and tissues; Fluorescence quantitative PCR (qPCR) and Western blotting (WB) were used to detect the expression changes of growth related factors in the two groups after 60 days, so as to explore the mechanism of Schizochytrium feeding on the growth performance in yaks. The results showed that, compared with control group, the body weight, chest circumference and slaughter rate were significantly increased (P < 0.05), the expression levels of serum growth related hormones GH, T3 and T4 were significantly increased (P < 0.01), and the growth related genes (Ampkα1, Mc4r, Lxrα, Lkb1) and growth related protein (AMPKα1) were significantly up-regulated (P < 0.01) after Schizochytrium feeding in yaks. In conclusion, Schizochytrium feeding increase the growth hormone levels, via regulates the expression of growth related factors and promotes their growth and development performance in yak, which provides a certain theoretical basis for yak breeding and feed improvement.