People-counting systems for image acquisition are usually complicated and expensive. In this paper, with detailed analysis of the pyroelectric effect and infrared sensor, BISS0001 integrated signal processing chip were chosen to design an amplifier circuit for the RE200B pyroelectric infrared sensor, in order to study its output waveforms under various human movement states. A people-counting system was designed, with double pyroelectric infrared sensors as the signal acquisition unit and a Cortex-M3 microcontroller as the control core, and its main algorithms were researched. The experimental results demonstrate that different body movement states can be accurately characterized using the output waveforms of the RE200B pyroelectric infrared sensor and the movement directions can be precisely distinguished by the people-counting system based on double pyroelectric infrared sensors designed in this paper. Furthermore, the system realizes real-time counting, and can be applied to a wide range of areas including human body detection and counting.