Respiratory frequency and mode could be applied for medical diagnosis and health evaluation. Traditional medical diagnosing devices have bulky size and high cost, and are of inconvenience in use. To fulfill the urgent demand for high-performance, low-cost, and portable electronic devices, this study proposes to fabricate self-powered planar humidity sensors by inkjet-printing method by virtue of the characteristics that graphene oxide self-polarizes and is sensitive to humidity. This sensor linearly responds to the relative humidity, and both responds and recovers rapidly. In addition, this sensor possesses excellent sensitivity and stability after multiple cycling and long-term storage, and has realized monitoring of the respiratory frequency and mode. The humidity sensors in this work is ready to fabricate with low production cost, free from interference by body motion or exterior environment, and suitable for real-time monitoring respiratory frequency and mode.