A novel dielectric-loaded surface plasmon polariton (DLSPP) waveguide with an air nanohole within a high-index dielectric ridge is proposed and analyzed. It is demonstrated by simulations that the introduced air nanohole could strongly modify the modal behavior, and it could alleviate the transmission loss caused by the high-index ridge with rather small sacrifice in the mode area. Under certain geometric parameter ranges, a shallow and wide air nanohole at the metal surface could result in strong local field enhancement while improves the figure of merit (FOM). The proposed structure could enable the realization of the DLSPP waveguide with a high-index ridge to achieve subwavelength mode confinement with relatively low transmission loss.