Visualized experiments were conducted by using a high speed video camera system to study slug flow in a narrow rectangular channel(3.25 mm×40 mm)with four inclination angles.For low two-phase superficial velocity

due to buoyancy slug nose deviated from the channel centerline and became sharper under inclined condition

resulting in the increase of slug velocity.The coefficient C0 decreased with increasing inclination angle

while drift velocity V0 varied inversely.For the case of high two-phase superficial velocity

the influence of inclination angle on slug velocity weakened with the flow tending to be stable

as was the same to C0 and V0.Four classical correlations for calculating slug velocity were evaluated against the experimental data.The correlations of C0 and V0 were given according to the threshold of 3.5 of Froude number.