The invention discloses a method for modifying activated carbon-based propane adsorbent with trace potassium hydroxide. One-piece coaly activated carbon is vertically immersed in 1mmol/L to 100mmol/L of diluted potassium hydroxide solution for 10 minutes, turned over to be immersed again for 10 minutes and then taken out, an air compressor purges the coaly activated carbon to remove the redundant potassium hydroxide solution, and after drying in a 50DEG C blast drying oven, the activated carbon-based propane adsorbent is obtained. The propane adsorption property of the obtained activated carbon-based propane adsorbent is greatly improved in comparison with the propane adsorption property of unprocessed coaly activated carbon. The method has the characteristics of easy material obtainment, simple process and low cost and a good application prospect.