Abstract: Affected by the instability of mixed light oil and the poor mixing effect of thin and heavy oil, the ultra-heavy oil electric submersible pump in Tahe oilfield was characterized by extremely unstable operation condition, more fault shutdown times, low running life and difficult to develop the well reserves by the current technical level, which oil viscosity is more than 100 × 104 mPa·s and viscosity-temperature inflection point is deeper than 3 500 m. In order to improve the pump operating condition, extend the running life and increase the reserves of ultra-heavy oil produced by mechanical lifting. From the aspects of improving the dilute heavy oil mixing effects and ensuring super heavy oil could smoothly enter into the pump, a pump installed tail pipe device was developed, and was applied in five wells in field. The results show that: the device is able to enhance dilute heavy oil mixing effects, improve the pump operating condition and produce ultra-heavy oil reserves. The pump has broad application prospects in the heavy oil wells.