Accurate measurement of canopy gas exchange rates is crucial for studying canopy photosyntheticresource use efficiencies. We designed, created, and evaluated a new canopy photosynthesis and tran-spiration measurement system (CAPTS). The CAPTS included: (1) modular chamber sides, (2) sensors fortemperature, CO2, air pressure and humidity that were integrated on a removable chamber cover, and(3) a user-friendly console for control of automatic opening and closing of the chamber cover for datarecording, storage and analysis. The CAPTS can accurately measure canopy photosynthetic CO2uptakerate, which was demonstrated with both rice and tobacco. The CAPTS provides a basic ability to measurerates of photosynthesis, respiration, and transpiration of plot-size canopies and other components ofagro-ecosystems