A rib waveguide structure in As2Se3 chalcogenide glass has been designed and numerically analyzed for on-chip coherent supercontinuum generation in the midinfrared region. The waveguide structure possesses an all-normal dispersion profile with dispersion value of -13.22 ps/nm·km at the pump wavelength. Coherent midinfrared supercontinuum spectrum spanning 1.2 to 7.2 μm has been obtained using a 2.5 mm long rib waveguide when pumped with 200 fs laser pulses of a peak power of 2.5 kW and a repetition rate of 1 kHz at 2.8 μm. Such highly nonlinear subwavelength size rib waveguide structures are highly applicable for the power efficient on-chip midinfrared coherent supercontinuum sources. Coherent midinfrared supercontinuum sources are very important in frequency metrology, nonlinear microscopy, nondestructive testing, molecular spectroscopy, and optical coherence tomography.