Dual-wavelength lasers with high power and high beam quality are critical to the applications such as precision spectroscopy, resonant interferometry, lidar, etc. However, limited by the intrinsic spectral and gain characteristics of currently available laser gain materials, it is difficult to realize high-power dual wavelength lasing directly from inversion lasers. To overcome this problem, nonlinear optical frequency conversion has been applied to convert the high-power laser in a conventional band to another or several hard-to-reach bands. As a third-order nonlinear effect, stimulated Raman scattering has advantages including large frequency shift, self-phase matching, and beam clean-up effect that lead to Raman laser an effective means to achieve high efficiency and high beam quality wavelength conversion. In this paper, diamond crystal that with a wide spectral transmission range (>0.23 μm), ultra-high thermal conductivity (>2 000 W·m^-1·K^-1) and large Raman frequency shift (1 332 cm^-1) was used as the Raman gain medium. By using a 1 μm laser as pump source, dual-wavelength lasing at 1.2 and 1.5 μm was achieved based on an external cavity Raman oscillator. With a maximum steady-state pump power of 414 W, output powers up to 72 W at 1.2 μm and 110 W at 1.5 μm were obtained. This study has opened a new way to realize high-power dual-wavelength laser output.