A kind of salt-based colloid palladium of high concentration was prepared,with concentration up to 3.6g/L on amount of PdCl2.The optimal preparation conditions of the salt-based colloid palladium were that the PdCl2and NaGl concentrations were respectively 3.6g/L and 175g/L,mole ratio of Sn to Pd was 50:1,reaction temperature was 20-35 ℃,with urea,ascorbic acid and vanillin added in a proper amount.The test results of optimal condition show that the time of starting hydrogen-deposition is 9 s,the time of completely coating copper on a test substrate is 2 min,the stability time of colloid palladium is 98 h after it is diluted into 0.1g/L(on amount of PdCl2)when the solution temperature is 20 ℃,the backlight lever of electroless copper plating layer is 10th grade of 10-grade system,the adhesion force of the copper layer is up to GB5270-85 of China,and the average particle size of the colloid palladium is 81 nm measured by Master Sizer.