Bedside care that relies on manual monitoring of sleeping posture is inefficient. To automatically collect accurate sleeping posture information, improve user experience and protect user privacy, a simple, low-cost, high-precision and high-speed sleeping posture monitoring system based on flexible pressure sensing array is designed by combining theoretical analysis and experimental research. Theoretically, according to the similarity between tactile and visual recognition mechanism, the influence of pressure image resolution on the classification effect of sleeping posture is revealed. The 24×24 scale threshold of pressure sensing array is further obtained by analyzing a public dataset, which significantly reduces the cost and complexity of the system. Experimentally, the sleeping posture monitoring system is designed based on 3 modules: Flexible pressure sensing array, signal scanning acquisition circuit and sleeping posture recognition algorithm. Firstly, the piezoresistive sensing array is designed based on flexible pressure-sensitive conductive sheet Velostat. Secondly, the anti-crosstalk signal acquisition circuit is arranged based on the zero-potential array scanning method. Thirdly, the sleeping posture classifier is trained with improved residual network. After experimental testing, the recognition accuracy for 8 types of sleeping posture is 99.57%, and the monitoring rate can reach 150 ms/frame. The system is expected to be commercially used for reliable real-time sleeping posture monitoring.