Abstract We design a self-collimated surface mode photonic crystal (PhC) W1 waveguide, and integrate it with an improved PhC T-junction to generate a self-collimated 1×2 TM-polarized beam splitter. On the basis of the detailed study of the surface mode of PhC without corrugations and with corrugations, the physical mechanism of self-collimated effect using periodic corrugated PhC is explained. As far as we know, this is the first time that such kind of device is presented. We further validate the self-collimated effect using the finite difference time domain method. From its far field, no beaming is observed, and the half width angle is as low as 3.68 degree which demonstrates the self-collimated phenomena of our designed device. Furthermore, our design demonstrates the possibility of integration of different PhC devices, and can be easily extended to other TM-polarized beam splitters.