Considering the importance of the respiratory signal detection in the sleep state,a breathing signal sensor device for detecting respiratory signal is developed based on the piezoelectric effect of polyvinylidene fluoride (PVDF). The front part of the sensor device is composed of polyvinylidene fluoride (PVDF) piezoelectric film and scalable belt.To obtain a stable respiratory signal,a flexible structure is placed between the sensor and the belt. Flexible signal processing modules with high quality are designed for extracting output respiration signals from sensor. Test results show that the detected respiratory signal waveform presents with recurrent form with good stability, meeting the requirements of actual testing.