This paper introduced a new dual-frequency millimeter-wave Doppler radar （YBJ-DFDR， W band 94 GHz， wavelength 3.2 mm， Ka-band 35 GHz， wavelength 8.6 mm） situated at Yangbajing in the Tibet Plateau and presented detailed analysis of the detection capability through calculations and comparisons. The analysis results show that the DFDR has a high sensitivity with -39.2 dBZ and -33 dBZ at 10 km for the W-band radar and Ka-band radar， respectively. It is shown that the radar equivalent reflectivity factor measured by Ka- and W—band radar illustrates various distribution characteristics for different cloud types. When rainfall occurs， W-band radar suffers much more attenuations by precipitation than the Ka-band radar （the difference between them reaches up to 30 dB in some cases）， further， the attenuations may cause the loss of the reflectivity of W-band radar. On the other hand， when the cloud particles are mostly ice particles， the attenuation effect significantly decreased， and W-band radar shows stronger detection ability than the Ka-band radar with higher reflectivity values. In addition， it is also found that Ka-band radar is prone to miss more cloud edge areas than the W-band radar， such as the cloud top and cloud bottom area， resulting in underestimation of the cloud top height but overestimation of the cloud bottom height. The main reason is that the cloud particles in these areas are small and number concentration is generally low， which has weak reflectivity lower than the sensitivity of the Ka-band radar.