Abstract: In allusion to running requirements of in-service pipeline and reduce pipeline safety risk, decrease economic loss and avoid environmental pollution, the technology in in-line demolishing L-O-R (Lock-O-Ring) flange's handle of oil & gas pipeline at 10 MPa (maximum pressure) is researched. According to calculation and experiment results, a comprehensive work process is formulated, including magnetic drill location and drilling, valve installation, checking of handle's leakage degree, tapping machine installation and handle demolishing. Detailed work method and requirements of every step are also presented. The work done in a pipeline in Southern China area showed that this technology was safe, reliable and operable. The method is considered that long-time shut-down and venting for pipeline can be avoided and has a good application prospects.