In situ ophthalmic gel is a gel preparation that is initially in the form of ophthalmic solution that dripped into the eye and then the solution turns into a gel after contact with the surface of the eye. In situ gel will undergo phase change to gel due to pH, electrolyte and temperature conditions. So that the preparation of ophthalmic in situ gel is required characterization to make sure that the prepared preparations meet the standards and are safe when used. Chemical evaluation includes pH, concentration, chemical bonds, crystallization and drug and polymer interactions. The purpose of this review is to discuss the evaluation methods used in preparations, and to see whether the pH of in situ ophthalmic gel formulation that provided can met the ideal pH requirements of the eye, so that the ophthalmic in situ gel preparation would not causing irritation and liquid tear production.