With Tomato ‘Liaoyuan Duoli’ as the materials of this experiment, using the mode of nutrient solution cultivation, the compared seedlings was cultivated as normal temperature as 15 ℃ of nighttime, set the temperature of nighttime as low as 6 ℃ to cultivate seedlings, we analyzed the factors affecting the absorption and transport processes of phosphorus of tomato seedlings in low night temperature. Results showed that: (1) the root activity of tomato seedlings was significantly inhibited by low temperature stress at night; (2) Under the condition of low temperature, there is no apparent change in the activity of acid phosphatase in the root of tomato seedlings, but the activity of acid phosphatase has strengthened in the aboveground parts and the activity of leaves increased significantly; (3) The relative expression of tomato phosphate transporter gene LEPT1 and LEPT2 increased in the roots by low temperature at night, LEPT1 phosphate transporter gene expression is suppressed in the aboveground, which is more apparent in leaves; (4) The P residue is higher than that in the control under treatment of low temperature stress at night; the concentration of phosphorus in the parts of seedling either underground or aboveground decreased, Such decline in the leaves is higher than that of the stems; (5) The bleeding intensity of tomato seedling decreased; P concentration in the bleeding sap increased with experiment period and significantly higher than that of control in the 9th day. These results showed that the root activity of tomato seedlings significantly decreased by low temperature at night; the low temperature made phosphate transporter gene LePT1 expression and the intensity of the bleeding sap decreased, which caused the transport of phosphorus from the stem to the leaf was inhibited.