The present paper proposes an optical chemistry sensor used for real-time detection of trace Cu2+, including the optical perception module and the signal processing module. The optical perception module gives the output of the laser light and excitation of fluorescence. The signal processing module completes optoelectronic conversion and amplification of the weak fluorescence signal as well as data processing and display. A self-developed optical acquisition, conversion and processing system was used to complete rapid detection of trace Cu2+, miniaturizing and reducing the cost of the testing instruments. The experimental results show the proposed sensor responds linearly in a concentration range of 30～1 000 nmol·L-1, with the linear equation y=0.109 77x+11.872 32, the linearity 0.994 82, the standard deviation 3.994 24, the detection limit 30 nmol·L-1, and the response time of the sensor 40 seconds. The experiment determines the interference of other ions with the Cu2+ test results. It shows that this sensor meets the demand of field detection for trace Cu2+ site testing.