Abstract: The axenic seedlings were cultivated to study the characters of development biology and the key planting technique of Citrus grandis Osbeck cv. Shatianyou Changshou in the period of seedling. The effect of light time on the growth of the seedling was mainly studied. The seedlings had been light on the 5th, 6th, 7th, 8th and 9th day. The growth in 30 days of underground and overground were compared respectively. The seedlings that grew best were the ones of being light on the 6th day. Every batch of these seedlings was transplanted on the 12th, 15th, 18th, 21th, 24th and 27th day. The seedlings that grew best were that been transplanted on the 18th, 21th, and 24th day, and there were no significant difference.