Two - phase flow is a stream of the most simple of multiphase flow. The basic characteristics of the two - phase flow include flow pattern and flow pattern maps, void fraction, and pressure gradient. On this research will be discussed about the investigation of pressure gradient on two - phase flow. Pressure gradient used on piping industrial world to know fluid pressure difference on the pipe. This research was on a glass pipe has a diameter of 1.6 mm with a slope of 300. The fluid used was an air - water mixture and glycerin (GL) with a presentation of 0%, 10%, 20%, and 30%. This research was conducted to find out the effect of superficial gas velocity (JG) and liquid (JL) and the effect of viscosity on the pressure gradient. To get the data pressure gradient using a pressure transducer connected with the side in and out on the side of the test section. The result of this research shows that the value of the pressure gradient is affected by the amount of liquid or gas superficial velocity. Experience increased pressure gradient due to the influence of the JL on the range 0.879, 2.297 and 4.935 m/s by varying the JG (0 – 66.3) m/s and experience increased pressure gradient due to the influence of JG at range 1.941, 9.62 and 50 m/s by varying the JL (0.033 – 4.935) m/s. Viscosity also affects the pressure gradient, from data research results on glycerin 0%, 10%, 20%, and 30% by varying the JG = 4.935 m/s and JL = 0.207 m/s. It shows the increasing viscosity of the resulting pressure gradient then will be increased.