Abstract: The MWD of alkyd resins and its relation to the physical properties of the resins have been studied by means of HPGPC, VPO, acid value and Gardner's tube viscosity measurements. The resins were synthesized using solid acid as catalyst The results show that for both the resins obtained either with or without catalyst the MWD changes in similar way during thc esterification and log d (degree of distributione appears to have good linear relation with the degree of reaction. The good linear relation was also found between Mn and d, as well as between log η_G and M_w. The use of the catalyst greatly reduces the reaction time and temperature when the identical M_w and MWD are desired. The alkyd resins obtained catalytically have a better solubility and longer pot-life due to their lower viscosity. They have higher M_w and better drying properties and high hardness value in comparison with those obtained without catalyst.