The Flow patterns and Pressure Drop on Two-Phase Gas-Liquid Through sudden Contrction. The aim of this research is to describe the flow patterns and ressure drop on two-phase gas-liquid trough sudden contraction. It limits the contraction coefficient (S) into three variants S 0 8 S 0 6 and S 0 4. For describing the distribition and pressure drop it uses two-dimension line graphics. The result shows that (1) the flow pattern in horizontal contraction tends to shape separated flow meanwhile in vertical contraction it tends to shape homogenous inflated flow (2) the pressure on pipe surfaces before contraction surfase is bigger than those of ducting axis (3) the pressure on pipe surfaces sfter contraction surface is smaller that those of ducting axis (4) the pressere drop turn into bigger on bigger mass flux and mixtur quality (5) the pressure drop in homogenous flow is bigger than those of separated flow and (6) the difference average betwen calcuated and theoretical pressure drop is tess than 20% 9