Objective To prepare the folate receptor-targeted and paclitaxel-loaded ultrasound contrast agent (folate-poly(lactide-co-glycolide)-paclitaxel,FOL-PLGA-PTX) and to investigate its targeting and imaging performance in vitro.Methods Paclitaxel-loaded PLGA-COOH micmcapsules with a core of liquid perfluorocarbon (PLGA-PTX) were prepared using single emulsion technique and then conjugated with folate by carbodiimide method.The size,surface potential,entrapment efficiency and drug loading efficiency were measured by Malvern laser detector and HPLC.The connectivity condition of PLGA-PTX with folate and the binding rate of fluorescent antibody were detected by immunofluorescence staining and flow cytometry.The targeting performance of FOL-PLGA-PTX was checked after co-incubated with human SKOV3cell lines in vitro and compared with that of non-targeted group and free folic acid intervention group.In vitro experiments were performed to explore the effects of FOL-PLGA-PTX on the enhancement of ultrasound imaging after irradiation by high intensity focused ultrasound (HIFU).Two-sample t test and one-way analysis of variance were used to analyze data.Results The average diameter of FOL-PLGA-PTX was (244.43 ±13.32) nm,with the drug entrapment efficiency of (86.23 ± 1.23)％ and loading amount of (8.62±0.12)％.The binding rate of folate was as high as (98.49± 1.28)％.The connection rate of FOL-PLGAPTX on SKOV3 cells was higher than that of non-targeted group ((84.32±4.25) ％ vs (16.45±2.89) ％; F289.45,t=10.654,P＜0.01) and the free folic acid intervention group ((36.33±3.23)％; t=8.923,P＜0.01).During in vitro ultrasound imaging,the average grey scale of FOL-PLGA-PTX before HIFU irradiation was significantly lower than that after HIFU irradiation (39.32±3.64 vs 126.44±7.15 ; t =4.829,P＜0.01).Conclusion FOL-PLGA-PTX has been prepared successfully,with high entrapment efficiency and much drug loading,which can target to SKOV3 cells specifically and effectively in vitro,and enhance the ultrasound imaging greatly after HIFU irradiation.