Gas water heater, air-fuel ratio adjusting method and adjusting device of gas water heater and storage medium

The invention discloses a gas water heater, an air-fuel ratio adjusting method and device thereof and a storage medium, the gas water heater comprises a shell, a combustion system, a premixing system and a control system, and the combustion system comprises combustion chambers which are arranged in the shell and communicate with one another; the premixing system comprises a premixer, a fan and a nozzle which are arranged in the shell, the premixer is provided with a fuel gas flow channel and an air flow channel, an outlet of the fuel gas flow channel is communicated with an outlet of the air flow channel and serves as a premixing cavity, the premixing cavity is communicated with the combustion chamber, an inlet of the fuel gas flow channel is used for being communicated with an external fuel gas supply pipeline, and the air flow channel is used for being communicated with the fan; the nozzle is arranged on the fuel gas flow channel and is used for adjusting the flow area of the fuel gas flow channel; the cont