The utility model discloses a guard for condensing type gas water heater heat exchanger and is arranged on surface of a condensing type gas water heater heat exchanger. The utility model is characterized in that the guard is a coating structure on surface of a heat exchanger. The coating is a chemical plated nickel-phosphorus alloy coating. The coating can be dope or heat-resistant paint dominated by organosiliconpolymer; the dope can be either black cathodic electrophoretic dope primarily containing acrylic resin, epoxy, masked isocyanate resin in fatty group and a little alcohol ether solvent or cathodic electrodeposit. The utility model has the advantages of ensuring heat transfer by means of conduction and condensed fluid erosion resistance and so on.