Our previous investigations showed that retroviral gene transfer of tissue-type plasminogen activator (tPA) effectively targeted thrombolysis in vitro and in the model of inferior caval veins of rabbits. This study is to identify the target thrombolysis of retroviral vector recombinant pLEGFP-N1-tPA transferred into the tissue around the Dacron patch (the same materials making of the ring of mechanical valve) in left atriums of rabbits. 70 Dacron patches were transplanted into the left atriums of 70 New Zealand white rabbits. The rabbits were randomly divided into three groups according to the different handling methods, including local pLEGFP-N1-tPA transferred group (gene therapy group, 30 animals), pLEGFP-N1 transferred group (control group, 20 animals), medium DMEM + 10% neonate calf serum (NCS) injected group (blank control group, 20 animals). Samples of blood, Dacron pieces and left atriums (auricles) wall from half of above in each group were harvested on second day and another half were harvested on 75th day after surgery. The EGFP expression of harvested left atriums (auricles) wall were observed under the confocal. The thrombi on the surface of Dacron patches were detected by stereoscope and electron microscope. The tPA expression in left atriums (auricles) wall and in blood from left atriums were detected by Western blot and their thrombolysis and activities were observed and calculated in plasma plates. ELISA were used to identify the contents of tPA. No thrombus was seen on the surface of Dacron patches that were transplanted in left atriums by tPA locally transferring around them. Activity and content of tPA were high in local tissue of left atrium and in blood of left atrium. It demonstrated effectively thrombolysis by tPA rapidly, efficiently and long expressing. This puts the foundation of mechanical valve replacement model for tPA gene valve, next.