The invention discloses a waveguide formation method and an SF6 gas passive sensor comprising the waveguide. The waveguide formation method comprises the following steps: growing an insulation layer on a silicon substrate; spin coating photoresist on the surface of the insulation layer; photoetching the photoresist and forming a waveguide structure; carrying out vapor deposition of glass in the waveguide structure to form a glass waveguide layer; removing the photoresist that is not photoetched and the glass outside the waveguide structure through the stripping technology to form a waveguide main body; spin coating a polymer on the waveguide main body; photoetching the polymer and carrying out curing to form cavity pillars; and processing the tops of the cavity pillars through the bondingtechnology to form cavities, wherein the multiple cavities are connected to form a waveguide. The waveguide formation method and the SF6 gas passive sensor comprising the waveguide, through passive design, increase product life, improve sensor sensitivity and have a real-time online monitoring function.