A series of solid-acid catalysts with different content of components was prepared using the coprecipitation method. These samples comprised modified gamma-Al2O3 with phosphorus. The effects of various contents of phosphorus (Al/P ratio from 0.5 to 3) have been investigated to determine an optimum one. The samples were characterized using BET, TGA, XRD, and NH3-TPD techniques and were also tested in a fixed-bed flow reactor under the same operating conditions (T = 573 K, P = 16 barg, WHSV = 26.07 h(-1)). According to the experimental results, phosphorus-modified catalysts have shown better performance compared to pure gamma-alumina. It was found that surface areas increase with an increase in the molar ratio of aluminum-to-phosphorus. It was observed that aluminum phosphate samples with acidic sites whose acidity is very weak and/or moderate exhibit the best catalytic performance and stability. The sample with molar ratio of Al/P = 1.5 have exhibited the best activity for methanol dehydration.