Early diagnosis is primarily important for the therapeutic and prognostic outcomes of malignancies including prostate cancer (PCa). However, the visuality and veracity of ultrasound imaging for the diagnosis and prognostic prediction of PCa remains poor at present. In this study, we developed a new nanoultrasound contrast agent by modifying multi-walled carbon nanotubes (MWCNTs) with polyethylene glycol (PEG) and anti-PSMA aptamer. The result showed that the modified MWCNTs offered better visuality and veracity and were able to target PCa cells more effectively as compared with the traditional contrast agent. The zeta potential was about - 38 mv. The length of this contrast agent was about 400 nm and the diameter of it was about 30 nm. The zeta potential, TEM, and FT-IR all proved the successful preparation of the agent. The vitro cytological study revealed good cell uptake and biocompatibility of the new contrast agent. The minimum detection concentration in vitro is 10 μg/ml. The earliest stage of the detection was under the parameters of frequency = 6.0 MHz and medical index = 0.06. Both in vitro and in vivo ultrasound imaging demonstrated that the new nanoultrasound contrast agent had a good development effect, distribution, and metabolism, and may prove to be a good targeted ultrasound contrast agent, especially for PCa.