Abstract: To the general oil leaking problem in wellhead of viscous oil thermal recovery in Klamayi 6-9 tract, the followings are leaking cause analyzed, leak oil from slot, off-center abrasion of rod, wellhead installation and operating is not normalized that lead to rod and packing damaged, strength of sealing material isn’t enough and structure of packing box isn’t reasonable, crude oil viscosity and back pressure is high and so on.According to these factors, the way to treat oil leaking thoroughly is found, a new wellhead sealing technology-injection molding sealing technology is developed This technology make use of sealing space among packing box body and rod, use special injection molding gun to inject mew sealing material inside body, make balance between entry pressure of sealing agent and pressure of leaking oil medium.The technology set up a new seal structure to plug pore and pore path to prevent crude oil, water and gas leaking.Application on site shows it is convenient to operate new sealing device, practicability is strong.It can reduce energy waste and environment pollution caused by oil leaking, and have get good economic effect and social effect.