The nano-size Pb(Ⅱ)-phthalate was prepared with potassium phthalate and Pb(Ac)₂·3H₂O by ultrasonic liquid dispersion deposition method. The effects of reaction temperature,reactant concentration,dispersant quantity on particle size of Pb(Ⅱ)-phthalate were studied. The nano Pb(Ⅱ)-phthalate with particle size of 43 nm was obtained at 10 ℃ with concentration of 0.4 mol·L^-1,and dispersant quantity of 8%. Moreover,the catalysis of nano-size Pb(Ⅱ)-phthalate for double-base propellant (DB propellant) was studied. It is found that nano Pb(Ⅱ)-phthalate increases burning rate of DB propellant at 2-22 MPa and make DB propellant emerge mesa effect at 6-10 MPa. Compared with common Pb(Ⅱ)-phthalate,nano Pb(Ⅱ)-phthalate enabled the burning rate of propellant to be higher than that of propellant including common Pb(Ⅱ)-phthalate,and its pressure exponent is lower at 6-10 MPa.