Abstract: LDAR is a technology to discover and repair the process unit leakage of industrial production activities. Taking the VOCs leaked through valves of oil refining equipment in a refinery as an example, the leak detection of oil refining equipment and leakage volume calculation of VOCs have been conducted based on the LDAR technology. The statistical data shows that the main leakage parts are valve packing, adapting piece like flange, plug and joint, pump shaft seal, and open pipes like condensate and exhausting pipes. The calculation of leakage loss shows about a 400 t/yr of VOCs is leaked from the refinery which has a processing capacity of 500×10⁴ t/yr. The leakage sources which have a leaking detection result not less than 10 000 μmol/mol play a leading role in leakage assessment of oil refining equipment, and account for the major part of leakage loss from equipment. At the same time, repairment effect of leak points is assessed, which shows that the leakage loss of the refinery can be reduced by more than 50% by applying LDAR technology.