The aim of the present work was aimed to carry out comparative study between method (1) and method (2) for separation of cefixime trihydrate and its degraded products by using two different mobile phases, keeping the other parameters such as stationary phase, column condition, wavelength, and device. Mobile phase for method (1) consist of a solution of 0.03 M Tetra butyl ammonium hydroxide (pH 6.5) and acetonitrile with a ratio of 3:1 respectively while Mobile phase for method (2) consist of a mixture of 0.1 M sodium dihydrogen phosphate monohydrate solution (pH 2.5) and methanol with a ratio 3:1 respectively. To study the degraded products sample was subjected to Sun light, UV light, and thermal effects. From data obtained proved the method (2) gave less retention time for the separation of drug with a larger number of decomposed products being detected compared by method (1).