The purpose of this study is the development of analytical method for simultaneous determination of water-soluble vitamins (B1, B2, B3, B6, B9, B12 and vitamin C) in dietary supplement syrup, multivitamins and mineral dietary supplement syrup with iron, dietary supplement capsules and balanced supplemental nutrition for children by using gradient RP-HPLC methods with PDA detector. The separation of water-soluble vitamins was performed on waters Spherisorb ODS2 (250 mm×4.6mm, 5μm) column. The wavelength was 272 nm at room temperature and the detection limits ranged from 2.4 to 8.3 ng/µl. The average recovery was 98%-102 % and correlation coefficient (r) was 0.9992 to 1.