To clarify whether stand age can affect nitrogen (N) acquisition strategies by plants, inorganic and organic N uptake by Chinese fir (Cunninghamia lanceolata) plantation at three growth stages (five-year old for young plantation forest; thirteen-year old for mid-aged plantation forest; thirty-year old for mature plantation forest) was measured in Qianyanzhou Ecological Experimental Station with a short-term ¹⁵N labeling experiment. We found that stand age altered nitrate uptake by Chinese fir, the mature trees demonstrated the highest uptake rate ((5.72±0.24) μg N g^-1 d.w. root h^-1 d.w. root h^-1), while the trees at the middle age ((1.57±0.13) μg N g^-1 d.w. root h^-1) showed the similar uptake rate to the youngest (2.36±0.22 μg N g^-1 d.w. root h^-1). Uptake rates of ammonium for the mature trees ((34.33±1.20) μg N g^-1 d.w. root h^-1) and the youngest ((34.18±2.32) μg N g^-1 d.w. root h^-1) were similar and significantly higher than for the mid-aged trees ((23.33±1.39) μg N g^-1 d.w. root h^-1). Uptake of glycine by the Chinese fir was not affected by their ages. We concluded that Chinese fir trees prefer to take up ammonium, and uptake rates of nitrate for the mature trees were significantly lower than ammonium but higher than glycine. These findings reflect that stand ages can affect their uptake of inorganic N not of organic N and Chinese fir preferentially take up ammonium, showing the lower uptake rates of nitrate and glycine. This suggests that wood production could be greatly improved if N forms are considered for fertilization of Chinese fir.