Abstract: In order to meet the requirement of high output power of the laser monochromatic light source in the precision measurement, a high-power iodine stabilized He-Ne laser system with a fully enclosed, integrated structure was developed. The principle of saturation spectral detection, the method of absorption peak recognition and locking and the frequency stability of iodine stabilized laser were studied. Firstly, the basic principle of detecting saturation absorption spectrum of iodine molecular using the three harmonic method was introduced, and its mechanism of eliminating the power background was analyzed. Then, the stability of the integrated resonant cavity in the iodine stabilized laser was demonstrated, and the effects of axial expansion and lateral asymmetric deformation on the output power were discussed in detail. After that, the correspondence between the profile of laser output power and the iodine molecular saturation absorption peaks was presented, the feasibility of using the secondary harmonic signal to achieve absorption peak recognition was introduced, and the long-term locking ability of high-stability resonant cavity was demonstrated. Finally, the wavelength stability and reproducibility of high-power iodine stabilized He-Ne laser were analyzed. The experimental results showed that the standard deviation for the frequency jitter of high-power iodine stabilized He-Ne laser was 33 kHz, the stability at 1 000 s and the reproducibility in three months were 4.1×10⁻¹³ and 3.3 kHz (7.0×10⁻¹²), respectively. Its absolute frequency was 3.0 kHz lower than the recommended value by the International Committee for Weights and Measures (CIPM).