Laser basedphotoacoustic technique applied to trace gas measurement has proved to be a high sensitivemethod. The implementation of the computer control and data processing system makes themulti-component analysis and long-time continuous measurement of the photoacousticspectrometer available, and it also increases the sensitivity and reliability of thespectrometer. System performance measurement shows that the detect limit for ethyleneconcentration of 14×10-12 and the accuracy of 2% are reachable. As anapplication of the system to biological study, an experiment on monitoring of the ethyleneproduction from apple and cherry tomato fruit in anoxia and post anoxia condition has beencarried out.