In order to solve the measurement and integration of ZnO temperature sensor, a spectrum observation system is designed. Its spectrum range is 350～450 nm and resolution is approximately 0.1 nm. A reasonable optical structure is selected. Optical elements and light path are calculated and the aberration of system is eliminated to achieve the requirements of narrow spectrum range and high resolution. The system volume is 111 mm×83 mm×30 mm, satisfying the requirement of integration. And it can be used for further optimization, tolerance analysis to meet the processing requirements.