An experiment investigation of steam flow resistance across horizontal falling film tube bundle was carried out.Experiments were performed to simulate the flow process in a large horizontal falling film evaporator of MED desalination plant under the pressure from 12 kPa to 31 kPa and at the corresponding saturated steam temperature from 50℃ to 70℃ respectively.The results indicated that pressure drop of steam flowing across tube bundle with falling film was far greater than that through a plain tube bundle.Pressure drop coefficient not only was affected by vapor Reynolds number but also changed significantly with spray Reynolds number.From the experimental results a flow resistance correlation for steam flowing across horizontal tube bundle with falling film was proposed.