In this work, The complexation reaction between 5-(2-hydroxybenzylidene)-1,3-dimethylpyrimidine-2, 4, 6 (1H, 3H, 5H)- trion(L) with Cu+2, Co+2, Ni+2 and Zn+2 ions were studied spectrophotometrically in acetonitrile solution. The metal- ligand mole ratios and the stability constants of the complexes were determined using a spectrophotometric method at 25°C and ionic strength (0.01M) in acetonitrile. The stoichiometry of the complexes is established 1:1 by jobs and mole ratio methods. The formation of the complexes was also confirmed by IR and 1HNMR spectrometry. Formation constant evaluated from a non liner least square program KINFIT. The stability of the resulting complexes varied in the order Cu2+>Co2+>Ni2+>Zn2+.