In this communication, the sub-micron size polycrystalline silicon (poly-Si) single mode waveguides are fabricated and integrated with SiON waveguide coupler by deep UV lithography. The propagation loss of poly-Si waveguide and coupling loss with optical flat polarization-maintaining fiber (PMF) are measured. For whole C-band (i.e., λ~1520-1565nm), the propagation loss of TE mode is measured to ~6.45±0.3dB/cm. The coupling loss with optical flat PMF is ~3.4dB/facet for TE mode. To the best of our knowledge, the propagation loss is among the best reported results. This communication discusses the factors reducing the propagation loss, especially the effect of the refractive index contrast. Compared to the SiO2 cladding, poly-Si waveguide with SiON cladding exhibits lower propagation loss.