At present, humidity sensors have promising prospects in disease monitoring, family life, environmental protection, and so on. Flexible humidity sensor is more and more popular because of its flexibility and portability. In our work, a flexible humidity sensor based on a tin disulfide (SnS) nanoflower and a zinc stannate (ZnSnO) hollow sphere film was fabricated though layer-by-layer self-assembly technique. The humidity performance showed that the SnS/ZnSnO hybrid film sensor was ultrasensitive to humidity at room temperature. The test results demonstrated superior response, fast response/recovery behavior, and excellent repeatability. Moreover, compared to the single SnS and single ZnSnO nanomaterials, the SnS/ZnSnO hybrid film sensor exhibited great improvement in humidity sensing. In addition, complex impedance spectroscopy was adopted to further explore the sensing mechanisms of the SnS/ZnSnO hybrid to various humidities. Human respiration, palm sweat, urine, and water droplets were delicately detected by the SnS/ZnSnO humidity sensor, indicating its great potential in multifarious application fields.