The collection of atmospheric data plays a key role in the control of small unmanned rotorcraft flight. An atmospheric data acquisition system for the acquisition device of a small unmanned rotorcraft was designed by a digital MEMS sensor and TMS320F28335 chip based on the flight control needs of small unmanned rotorcraft. The space velocity required to control the flight of the unmanned rotorcraft is calculated in real time by collecting data with the sensor, and some algorithms such as linear interpolation are used to improve the calculation performance. The system can meet the needs of small unmanned rotorcraft because of its small size, low power consumption, and strong anti-interference ability, which has made some theoretical work for the practical application of small unmanned rotorcraft data acquisition system.