A method for realizing the micro audio directional loudspeaker in mobile phone is investigated to examine a novel auditory experience in this paper. This novel directional loudspeaker can provide private listening service by emitting the audible sound with high directivity along propagating axis. A prototype using Nokia N73 mobile phone as the package is constructed in which the emitter array is assembled by four PZT ceramic ultrasonic transducers with the diameter of 10mm. The emitter array is driven by a class D amplifier. The modulation algorithm is realized on a DSP platform on which the carrier frequency is equal to the resonant frequency of the emitter array. The testing results of impedance, frequency response and sound pressure level characteristics are described and analyzed. The directivity angle and power consumption of the prototype are measured. The experiment result indicates that the prototype size, power and the acoustic pressure level can satisfy the requirements for the mobile phone, thus the micro audio directional loudspeaker can be used for the portable multimedia devices.