The invention discloses a control method of gas water heater and a gas water heater. The gas water heater comprises a draught fan. The control method of the gas water heater comprises the following steps that the running duration of the gas water heater is acquired; judging whether the running duration is locate a preset range; under the condition that the running duration is locate the preset range, whether the output value of the draught fan is equal to the preset output value or not is judged; the preset output value is related to the preset range; when the output value of the draught fan is not equal to the preset output value, and the output value of the draught fan is adjusted according to the preset output value. Therefore, the output value of the draught fan is adjusted through therunning duration of the gas water heater, so that the operation of the gas water heater is more suitable for the environment, so that the gas water heater can be more accurately controlled, and the problem that the system control deviation of the gas water heater is poor is avoided or reduced.