With direct current reactive magnetron sputtering method，transparent conducting molybdenum-doped ZnO （ZMO） thin films with different carrier concentration on glass substrate were fabricated by monitoring oxygen partial pressure. The dielectric responses of the ZMO films are characterized with terahertz time-domain spectroscopy. Frequency dependent conductivity，power absorption，and refractive index are obtained，and the experimental results can be well reproduced with classic Drude model. Our results reveal that，by adjusting the carrier concentration of ZMO film，the conducting ZMO film can serve as broadband antireflection coatings for substrates and optics in terahertz frequency range.