ABSTRACT Objective To investigate the thrombolytic effect of EKOS? combined with intraclot injection of microbubbles (MB) and urokinase (UK). Methods The peak negative pressure（PNP）of the EKOS? catheter was measured using a hydrophone. Ninety thrombus samples were randomly divided into six groups：ultrasound（US）+MB+UK, US+UK, US+MB, US alone, UK alone and control group. The thrombolysis rate was measured via the mean clot weight loss and compared between groups. Residual clots were histologically observed with hematoxylin-eosin staining and immunofluorescence. Results The PNP of EKOS ? catheter shift irregularly within the range of 0.4-6.4 MPa. The thrombolysis rate of US+MB+UK（41.9±4.5）％ was similar to that of US+UK（42.0±3.3）％, which were significantly higher than that of the other groups ( P <0.05). Histological examination of the clots in US+MB+UK and US+UK showed that the interfaces of clots contacting with EKOS ? catheter were more disintegrable, and the distribution of red blood cells was sparser than other groups. The thrombolysis rate of US+MB (28.4 ±3.3) ％ was close to that of UK alone (27.8±3.1) ％ and significantly higher than that of US alone (23.9 ±3.0) ％ and control group (17.5±3.7) ％ ( P <0.05). Conclusion EKOS? catheter can obviously improve the thrombolysis rate of UK, however, including MB has no significant effect on thrombolysis rate.