The invention discloses a multifunctional gas water heater. The gas water heater comprises a water heater body, a heat exchanger mounted on the water heater body as well as a water inlet pipe and a water outlet pipe which are connected with the heat exchanger. The gas water heater is characterized in that a three-way valve is connected onto the water inlet pipe and divides the water inlet pipe into two branches, a water pump is arranged on one branch of the water inlet pipe, a water purifying and softening device is arranged on the other branch of the water inlet pipe, and ion exchange resin and activated carbon are arranged in the water purifying and softening device. Compared with the prior art, the gas water heater has the advantages that the water purifying and softening device is arranged, water scale production is effectively inhibited, and pipe blockage, especially blockage of a shower head, is avoided; meanwhile, the ion exchange resin and the activated carbon are arranged in the water purifying and softening device, hard water becomes soft water after passing through the ion exchange resin, the soft water contains little calcium magnesium salt and is smooth, and the bathing effect is better; the activated carbon purifies the water effectively, removes impurities and dirt, inhibits bacterium breeding and creates a safe, healthy and comfortable bathing environment.