Concentrations of major inorganic ions (NH 4 ,Mg,SO 4 ,NO 3 ,NO 2 ,Na,Ca,HCO 3 ,F,Cl,Br,K), PH, Total Dissolved Solids (TDS), Electrical Conductivity (EC), Total Alkalinity and Total Hardness in bulk precipitation samples collected in the Tehran city of I.R. of Iran were analyzed. Results show that concentrations of the found substances were higher over the Mehrabad station. The mean concentration of ions indicated that, HCO 3 , SO 4 and NO 3 and were the main anions, while Ca ,Na,NH 4 and Mg were the main cations. Measured PH had shown that autumn and winter precipitation were mostly acidic while the spring and summer were mostly alkaline. The pH ranged from 4.6 to 8.1 with a mean of 6.3. The alkaline cations Ca and Mg and also Bicarbonate anion acted as acid neutralizers and buffered the acidity of rain. The Bicarbonate anion had the highest concentration, among all other ions, over both stations and plays an important role in reduction of the acidity of the rain water. Study upon the potential sources of the ions over Tehran by means of Correlation Analysis, Enrichment Factor and Principle Component Analysis indicate that existence of Qom salt lake and desert in the south of the city were the main source of the Ca,Mg,K and Na . There are anthropogenic sources for SO 4 ,NO 3 , NO 2 ,F, Br ion's. The other ions HCO 3 and NH 4 were from anthropogenic and dust origin.