A　time-domain　model　is　proposed　to　study　the　density　wave　instability　of　supercritical　water　in　parallel　multichannel　system.　The　present　model　splits　the　flow　domain　along　each　channel　based　on　the　collocated　mesh　method,　and　adopts　an　iterative　solution　to　solve　the　coupling　among　multiple　channels.　The　model　is　verified　firstly　by　the　experimental　data　obtained　in　open　literature.　After　that,　the　model　is　used　to　study　the　effect　of　the　key　parameters　on　the　density　wave　instability　of　supercritical　water　in　parallel　multichannel　system　(such　as,　adding　different　perturbations,　inlet　fluid　temperature,　and　so　on).　Moreover,　the　influence　mechanisms　of　these　key　parameters　on　the　density　wave　oscillation　of　supercritical　water　are　also　explained.　It　is　found　that　out-of-phase　oscillation　occurs　between　the　perturbation　channels　(which　are　added　with　the　perturbation)　and　the　rest　other　channels,　and　the　amount　of　perturbation　channels　has　little　effect　on　oscillation　period　and　system　stability.　The　system　stability　first　decreases　and　then　increases　with　the　inlet　fluid　temperature,　and　the　system　has　the　worst　stability　when　the　inlet　fluid　temperature　is　equal　to　a　critical　value,　denoted　by　Tin-cr.　This　is　because　that　the　variation　of　the　fluid　density　along　the　system　will　reach　the　maximum　when　the　inlet　fluid　temperature　is　near　Tin-cr,　which　makes　the　system　most　unstable.　Tin-cr　is　always　lower　than　the　pseudo-critical　temperature　of　supercritical　water　at　the　corresponding　pressure.　Tin-cr　has　no　obvious　change　with　system　pressure.　©　2018　Elsevier　B.V.