A backpack sprayer includes a housing, a spray nozzle assembly, a fan assembly and a switch assembly. The housing is configured to contain a liquid. The spray nozzle assembly is communicated with the housing, and is configured to spray the liquid out from the housing. The fan assembly is connected to the spray nozzle assembly, and is configured to provide the spray nozzle assembly with power to spray the liquid out from the housing. The switch assembly is connected to the spray nozzle assembly and electrically connected to the fan assembly, and is configured to control opening and closing of the spray nozzle assembly and start and shutdown of the fan assembly simultaneously.