An ultrasonic irradiation route (USI route) is developed to synthesize whisker-like copper sulfide (Cu9S8) nanocrystals via the reaction between copper sulfate pantahydrate (CUSO4.5H(2)O) and thioacetamide (CH3CSNH2) in an aqueous solution at room temperature under ambient pressure. XRD, TEM, UV-vis and PL spectra are used to characterize the obtained product. A possible reaction process is suggested in the end of this paper.