This　study　reports　on　the　photooxidation　of　antiepileptic　drug　primidone　by　direct　UV-C　irradiation,　UV-C/H2O2,　and　UV-C/Fe(II).　The　influence　of　different　parameters,　such　as　pH,　hydrogen　peroxide　concentration,　Fe(II)　concentration,　Cl-　concentration,　HCO3-　concentration,　and　primidone　initial　concentration,　has　been　studied.　Experiments　were　carried　out　by　utilizing　a　UV　high-pressure　mercury　lamp　with　254　nm　wavelength　to　irradiate　aqueous　solutions　of　primidone.　Kinetic　experiments　showed　that　primidone　followed　pseudo-first-order　kinetics.　H2O2　concentration　and　Fe(II)　concentration　had　significant　influence　on　photodegradation　speed　of　primidone,　and　their　optimal　concentrations　were　1　and　0.1　mM,　respectively.　According　to　results　of　photooxidation　experiments,　effectiveness　of　specific　photooxidation　processes　could　be　arranged　in　the　following　order:　UV-C/Fe(II)＞UV-C/H2O2＞UV-C.　Optimum　conditions　for　primidone　UV-C　and　UV-C/H2O2　photodegradation　were　observed　at　a　pH　value　of　6.3.　Increase　of　concentration　of　Cl-　in　UV-C/H2O2　system　slightly　increased　primidone　degradation　rate.　However,　presence　of　HCO3-　inhibited　photodegradation　of　primidone.　Saturation　of　primidone　aqueous　solution　with　O-2　proved　to　be　beneficial　to　degradation　of　primidone　in　UV-C/Fe(II)　system.　Phenobarbital,　4-hydroxyphenobarbital,　and　1-(2-nitrobenzyl)-5-oxoproline　were　identified　by　liquid　chromatography-mass　spectrometry-mass　spectrometry　analysis　as　main　by-products　of　primidone　degradation.　Finally,　primidone　and　its　by-products　were　subjects　to　complete　mineralization　to　ammonia,　carbon　dioxide,　and　water.　This　study　obtained　the　fundamental　data　on　the　UV　degradation　efficiency　and　the　by-products　of　primidone,　and　data　obtained　in　our　study　can　be　used　to　evaluate　the　application　of　advanced　oxidation　processes.