Here, Ce-doped ZnO flower-like nanosheets are prepared by one-step hydrothermal method. The sensor based on Ce-ZnO composite exhibits excellent gas-sensing properties to acetone. Compared with pure ZnO, the response of Ce-ZnO composite is increased by 5.5 times, and the optimum operating temperature is reduced by 60°C. The gas-sensing properties of the sensor to acetone under different humidity conditions are investigated. The redox reaction of Ce element increases the anti-humidity of Ce-ZnO sensor. Finally, the gas sensing mechanism of Ce-ZnO nanomaterial and anti-humidity principle are discussed in detail. The result can provide a new material for develop high sensitivity acetone sensor and a new anti-humidity strategy for designing gas sensing materials.