Abstract: The kinetics and the influence factors of complex precipitation of DNA with Mn⁺⁺, Ni⁺⁺and Cu⁺⁺were studied by the laser scattering. The influence factors are M/P, concentration, pHand t(℃) etc. The experiments obtaining the active energies of the reaction, the complex ratio and the reaction order were also done. And the active order which was derived from active energies for complex precipitation is Mn⁺⁺<Ni⁺⁺<Cu⁺⁺, which is accord with the result from CFT. The presence of small ions Na⁺, K⁺, etc. plays, indeed, a important role in the formation of complex precipitation. The mechanism of complex precipitation was also analysed.