In recent years, ELISA technology has been developed rapidly and full-automatic ELISA analyzer, which is of significant practical value is widely used in the diagnosis of many diseases, such as, bacteria and viruses. Optical detection system is the hard core of fully automated ELISA analyzer and the key part of system is high-precision wavelength selector. The authors in this paper present the design of wavelength selector composed of light source, optical circuit plan, color filters and the module of signal acquisition. A control system for stepper motor which is used to choose the suitable color filters based on the microcontroller 8051 is introduced. From the results of experiment test, it can be seen that the wavelength selector is sufficient to meet the requirements of the full-automatic ELISA analyzer.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.