In order to extend the transmission distance of the traditional C-band high-speed optical module, this paper studies a kind of quasi-coherent reception technology based on the existing 25 Gbit/s optical module, and discusses the application scheme of the quasi-coherent reception technology. It is found that the quasi-coherent receiver can effectively reduce the influence of dispersion on the transmission distance of high-speed optical module without using additional electrical or optical dispersion compensation technology. The experimental results show that the quasi-coherent receiver has strong processing ability for optical signals degraded by dispersion, and the use of the quasi-coherent receiver can significantly improve the transmission sensitivity of the optical module. The experimental results show that the quasi-coherent reception technology can extend the transmission distance of the C-band 25 Gbit/s optical module with traditional intensity modulation technology from 10 km to more than 25 km.