The effect of supply ratio of nitrogen (N): phosphorus (P) on P uptake and utilization in germinated Changbai larch (Larix olgensis Henry.) was analyzed in our research. The seedlings were cultivated in a greenhouse where fertilizers were supplied according to N∶P ratios of 1∶3, 1∶2, 1∶1, 2∶1 and 3∶1. Seedling morphology and biomass accumulation, P content and concentration of needles and roots were measured. The method of vector diagnosis was used to analyze the interactions among biomass, P content and P concentration. Some seedlings were cultivated in hydroponic solutions for six hours to detect their kinetic characteristics. Two inorganic N sources, NH₄⁺-N and NO₃^--N, were employed to create the same N∶P ratios in the greenhouse experiment with the P source of PO₄^3-, separately. The results showed that root biomass accumulation and diameter increased significantly with the increase of N∶P ratio (P=0.0027 and 0.10013, respectively). Compared to the N∶P ratio of 1∶1, the N∶P ratio of 3∶1 increased the fine root length, surface area and volume by 14% (P=0.0178), 21% (P=0.0004) and 5% (P=0.0009), respectively. Root P concentration, root P content and needle P content were not affected by N∶P ratios (P>0.05). However, needle P concentration was higher in N∶P ratio of 1∶2 than 2∶1 (P=0.0270) and 3∶1 (P=0.0014), but it was not significantly different from that in N∶P ratios of 1∶3 (P=0.0669) and 1∶1 (P=0.0804). In N∶P ratios of 2∶1 and 3∶1, P utilization index was higher than the N∶P ratio of 1∶2 by 84% (P=0.0002) and 37% (P=0.0014), respectively. With the increase of N∶P ratio, P uptake efficiency increased linearly. N∶P ratio positively correlated with P uptake efficiency (R²=0.978). Vector diagnosis indicated that, compared to the N∶P ratio of 1∶2, the N∶P ratio of 1∶1 resulted in a nutrient dilution while the N∶P ratios of 3∶1, 2∶1 and 1∶3 resulted in a nutrient deficiency for needles; the N∶P ratio of 2∶1, 1∶1 and 1∶3 resulted in a nutrient excess while the N∶P ratio of 3∶1 resulted in a nutrient dilution for roots. The activity of acid phosphatase of needles in the N∶P ratios of 2∶1 and 3∶1 was higher than that in the N∶P ratio of 1∶1 (P=0.0026) while the activity of acid phosphatase of roots in the N∶P ratio of 1∶2 was higher than that in 1∶1 (P=0.0003). In solutions containing NH₄⁺-N or NO₃^--N, the P uptake rate did not change among N∶P ratios (P=0.3247 and 0.0934, respectively). However, the P uptake rate linearly and positively correlated with the ratio of NH₄⁺-N∶P (R²=0.908), while there was no significant correlation between P uptake rate and NO₃^--N∶P ratios (R²=0.005). In solutions supplied with NH₄⁺-N and NO₃^--N, V_max and K_m were regressed to be 0.89 and 0.60 mmol/h/g FM and 0.15 and 0.03 mmol/L, respectively. In conclusion, for improving the efficiencies of P uptake and utilization of larch seedlings under the circumstance of both supplied N and P, nitrification should be avoided and the N∶P ratio should be increased within a certain range.