Amine Flash Drum is a processing unit in the H2S removal system. This unit is used to separate three kinds of fluids, namely rich amine, hydrocarbon and gas from the outflow of the amine contactor. The amount of each component is always changing at any time. Including rich amines whose solution density is very dependent on the amount of H2S and CO2 absorbed. Thus, if the amount of sour gas produced by the wellhead is reduced, the amount of H2S and CO2 gas produced will also decrease. Thus, the density of rich amine will also decrease. In this study, simulation is done by Simulink to get the quantity of hydrocarbon. The result show that when the number of hydrocarbons is very small and the moles of H2S and CO2 decrease by 2,869 and 7,076, the density will decrease to 1033.3 kg / m3 and cause an error in the measurement results of 4,945% or equivalent to 39.59 mm. Meanwhile, when the amount of hydrocarbons accumulated in the amine flash drum becomes very large, an error of up to 24.36% is obtained or the equivalent of 195.07 mm. Through simulation with simulink, a density recommendation that can be used for calibration is obtained which is 1089.65 kg / m3 which can reduce the measurement error to 2.56% or equivalent to 20.5 mm for the first operating condition and 2.7% or equivalent to 21.6 mm for the second operating condition.