Two kinds of novel dual-frequency He-Ne lasers and presented are described in this paper based on the birefringent laser frequency splitting technology:the full-inner cavity and the half-inner cavity photoelastic dual-frequency lasers.The frequency difference between the two kinds of dual-frequency He-Ne lasers can be adjusted from tens to hundreds of MHz by adjusting the mechanical pressure exerted on the photoelastic element.The stability of the frequency differences of the two lasers are 10 -3 and 10 -5,respectively,after the lasers are turned on for while.