A series of phosphorus (P) modified HZSM-5 catalysts were prepared and characterized with various techniques. These catalysts were used in dehydration of ethanol to ethylene at different temperatures. It was found that not all the P-modified catalysts favor this reaction at high temperatures. Over the catalyst with 3.4 wt% P, the main product is ethylene at 573-713 K, due to the presence of weak acid sites after P modification. When the P loading is below 3.4 wt%, ethylene and higher hydrocarbons are observed at high temperatures. As P content is above 3.4 wt%, higher reaction temperature is necessary for ethanol dehydration to ethylene.