Objective To study the effect of Maca extract on toxicity and immune organs in mice. Methods One hundred and fifty SPF BALB/c mice (male:female=1:1, body weight 20-22 g) were used in this study. The mice received Maca extract for 15 days, and the maca toxic effect on mice, and the thymus and spleen weights were observed. Results At 24 hours after oral administration of Maca extract in an accumulated dose of 320 g/kg·bw, no toxic response was seen in the mice. After administration of Maca extract in a dose of 16.0, 32.0, and 64.0 g/kg·bw for 15 days, the thymus weight was increased by 36.84%, 89.47% and 107.89%, respectively, the spleen weight was increased by 44.83%,62.01%, and 89.66%, respectively, the carbon clearance index was increased by 30.85%, 30.85% and 42.55%, respectively, and the serum hemolysin value was increased by 11.64%, 20.03% and 31.51%, respectively, in the experimental mice, significantly higher than those of the control group (P < 0.05 or P < 0.01 for all). Conclusions Maca extract exerts an enhancing effect on the immune organ weights and improve the immune function, and is associated with a lower toxicity.