Abstract: In order to increase the heat transfer performance of the falling film evaporator outside horizontal tubes，increasing inter-connection rib plate between horizontal tubes to strengthen the heat transfer was proposed. The heat transfer performance of the falling film evaporators outside horizontal tubes was studied with distilled water as working medium，the evaporative heat transfer coefficient of outside horizontal tube increased with the increase of sprinkling density，temperature difference and inter-connection baffle width，and reduced with the increase of diameter.