The effects of isochronal exogenously applied synthetic-GA3, fungal-gibberellic acid and different light on the sheath length of the second leaf of Oryza sativa L.cv.Tan-ginbozu were determined under controlled environmental conditions. Our results showed that the effect of fungal-gibberellic acid on the sheath length of the second leaf is higher than that on the control groups (group of 1/2N Hoagland culture solution and group of 1/2N Hoagland culture solution+methanol); however, synthetic-GA3 was more effective on the length of the second leaf than fungal gibberellic acid. Moreover, it was identified that the effect of red light is higher than that of fluorescent light on the growth of the second leaf. Our study has shown that red light and exogenously applied GA3 together have synergistic or supplemental effects on the sheath lengths of the second leaf of dwarf rice Tan-ginbozu.