In order to improve the efficiency of ultrasonic energy transformed from electricity for an ultrasonic transducer array, a novel 1/2 wavelength multi-hole broadband-based transducer was designed, developed and evaluated. The low equivalent mass of the transducer is realized in this work through drilling holes on the output end of the horn. In comparison with a traditional transducer, the developed transducer has demonstrated a lower mechanical quality coefficient and a wider broadband. As a result, an ultrasound treatment system for crude oil has been developed based on the new transducer design. Furthermore, we have demonstrated the effectiveness of the ultrasound treatment system on viscosity reduction of crude oil and paraffin.