【Objective】The dynamic change of phosphate-solubilizing ability of Pseudomonas vancouverensis strain PAN4 under different culture conditions and the effects of growth promotion and the photosynthetic characteristics of walnut, Juglans sigllata, seedlings were studied. 【Method】 The phosphate-solubilizing property was studied in liquid Pikovskaya medium (PVK). The influences of carbon source, nitrogen source, initial pH and temperature on phosphate-solubilizing of P. vancouverensis strain PAN4 were determined using a single factor test. The growth promoting effects on walnut seedlings were conducted in sterilized soil and unsterilized soil, respectively. 【Result and conclusion】 The available phosphorus content in supernatant of strain PAN4 significantly increased with time extending, with the maxium content of available phosphoru reaching a peak at 48 h. The malt and corn steep liquor was the optimal carbon source and nitrogen source, respectively. The maxium growth mass and the maxium phosphate-solubilizing ability were obtained at 28 ℃ under pH 7, and both had a significantly positive correlation. The increase of plant height, basal diameter, net photosynthetic rate, transpiration rate and chlorophyll content correlated with the concentrations: the higher the concentration, the more increases. The effect of compound fertilizer was less than those of the bacterial inoculant with the concentrations of 10⁸ and 10 ⁹ cfu·mL^-1. The growth promoting effect of the bacterial inoculant was better in unsterilized soil than that in sterilized soil.