The optical beat method can be used to measure the wavelength stability of frequency-stabilized He-Ne laser and evaluate the wavelength uncertainty. A portable wavelength evaluation system for 633 nm laser used in measurement site is reported. The principle of beat frequency measurement technology, the basic structure of laser wavelength evaluation system and the comparison results with non-portable traditional beat frequency system are introduced. The wavelength evaluation system improves the traditional optical beat optical path and integrates it into a portable measurement system. The system uses a newly designed integrated optical beat module, a miniaturized high-precision frequency meter and a spectrum monitoring instrument to achieve the generation, counting and monitoring of beat signal with high signal-to-noise ratio, and independently develops the beat measurement data acquisition, processing and analysis software. The experimental results show that the system can realize the stability and uncertainty evaluation of laser wavelength in the measurement site, and improve the convenience and efficiency of field measurement.