The planar waveguide lasers are the good combination of slab lasers and fibre lasers, which combine the advantages of both while avoiding their each disadvantages. The high aspect-ratio allowing for efficient one-dimensional heat flow from the active region, leads to controlling the thermal lens effect well and controlling the beam quality excellently. By increasing the width and length of the active-region, the high output power is obtained, and the waveguide structure which has a numerical aperture does a great job in constraining the non-diffraction limited pumping light, leading to the high brightness of the lasers. Introductions about the fabrication, materials and history of planar waveguide lasers are made. The reported studies relating to the planar waveguide lasers are reviewed, and the prospect of the further progress is given.