2-(6-Oxid-6H-dibenz[c,e][1,2]oxa-phosphorin-6-yl) 1,4-benzenediol (ODOPB) was prepared by the addition reaction between 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and p-benzoquinone while DOPO was synthesized through multistep reaction from o-phenylphenol and phosphorus trichloride. The compound (ODOPB) was used as a reactive flame-retardant in o-cresol formaldehyde novolac epoxy resin (CNE) for electronic application. Owing to the rigid structure of ODOPB and pendant P group, the resultant phosphorus containing epoxy resin exhibited better flame retardance, higher glass transition temperature and thermal stability than the regular bromine-containing flame-retardant epoxy resin. UL 94-VO rating could be achieved with a phosphorus content of as low as 1.1% (comparable to a bromine content of 6%) in the cured resin and no fume and toxic gas emission were observed.