To understand the growth adaptability and salt tolerance mechanism of Juniperus chinensis seedlings under NaCl stress, we investigated the cationic absorption and distribution in different organs (such as roots, stems and needles) of the raw J. chinensis seedlings and its biomass accumulation under different levels of NaCl (0, 100, 200, and 300 mmol·L^-1) stress through potted soil culturing in greenhouse. The results showed that: (1) with the increase of NaCl concentration, the growth including plant height, ground diameter, relative height growth and biomass accumulation were declined, while the root/shoot ratio was increased, indicating that the growth was inhibited; (2) under the NaCl stress, the Na⁺ concentrations in the roots, stems and needles of the J. chinensis seedlings were significantly increased compared with those of the contrast seedlings, and the Na⁺ concentration in the needles was significantly higher than that in stems and roots, the Na⁺ concentration in the needles was 5fold higher in the roots; (3) with the increase of NaCl concentration, the K⁺, Ca²⁺ and Mg²⁺ contents, K⁺/Na⁺, Ca²⁺/Na⁺ and Mg²⁺/Na⁺ ratios in different organs of the seedlings were decreased; (4) under the NaCl stress, the K⁺Na⁺ selective transportation coefficients (S_{K, Na}), Ca²⁺Na⁺ selective transportation coefficients (S_{Ca, Na}) and Mg²⁺Na⁺ selective transportation coefficients (S_{Mg, Na}) of the roots were significantly decreased, but the S_Ca,Na and S_Mg,Na of the stems and needles were generally decreased, while S_K,Na of the needles were significantly declined with the increase of NaCl concentration. And large amount of Na⁺ was retained in shoots, which was advantageous for reducing the damage of salt stress to roots. In conclusion, our findings suggested that the saltadaptation mechanisma of J. chinensis seedlings were primarily implemented by root growth stimulation, stems and needles Na⁺ accumulation, and are also correlated with a remarkably increased ability of K⁺, Ca²⁺ and Mg²⁺ selective transportation in roots and steadyability of K⁺, Ca²⁺ and Mg²⁺ selective transportation in stems and needles.