Abstract： Objective To prepare targeted nanoscale lipid ultrasound contrast agent and study the targeting function in vitro.Methods After the biotinylated monoclonal antibody Herceptin was prepared,the biotinylated degree and immunological activity were determined.Then biotinylated antibody was attached to the surface of nanoscale lipid ultrasound contrast agents by avidin-biotin system to prepare the targeted nanobubbles.The targeting function was studied by observing the combination ability of the targeted nanobubbles with SKOV3 cells in vitro,non-targeted nanobubbles as controls,and observing ultrasound imaging in vitro.Results About 16 biotin molecules were coupled to each antibody in average,and the immunological activity of the biotinylated antibody didn't decrease compared with the free one(P ＞0.05).SKOV3 cells were combined firmly and surrounded regularly by red dyed targeted nanobubbles,while control groups were negative.Ultrasound imaging could be significantly enhanced by targeted nanobubble binding to SKOV3 cell slides,the other two control groups were negative.Conclusions Nanoscale ultrasound contrast agent and antibodys can be combined firmly by avidin-biotin system to produce the targeted nanobubbles,which have strong targeting function in vitro and significantly enhanced ultrasound signal.