The invention relates to a gas 
water heater descaling device and a descaling method thereof. The gas 
water heater descaling device is characterized in that the 
chemical reaction principle is utilized, a 
descaling agent is added into a water tank of the gas 
water heater, the 
water temperature is raised and maintained to certain temperature through heating, a water pump is started to enable the water in the water tank to circulate, the 
descaling agent and the main components of the accumulated scale generate 
chemical reaction, then the firm accumulated 
dirt is loosened or dissolved, and the accumulated scale is cleaned. The gas water heater descaling device has the advantages that the 
descaling agent can react with the water scale in the circulating flowing process, the descaling efficiency is higher, the descaling time can be freely controlled, and the accumulated scale is more thoroughly cleaned at higher temperature; after the descaling agent is added, the concentration is controlled to be stable, the descaling agent is freely added to guarantee the proper concentration, and the reaction of the accumulated scale is favorably realized; the bulky water scale is fully dissolved, the cleaning effect is good, the heating surface is clean, the good 
heat transfer effect is realized, and the 
gas consumption is saved; the structure is simple, the convenience in use is realized, the safety and reliability are realized, the descaling efficiency is high, and the usage amount of descaling amount is saved.