Supercritical　carbon　dioxide　(scCO(2))　was　applied　for　the　first　time　to　post-treat　two　hydrothermally　synthesized　LiFePO4　of　H1　and　H2　to　entirely　alter　their　particle　size　and　morphology.　H1　had　the　morphology　of　platelets　aggregated　in　one　direction　in　size　of　about　20-30　mu　m,　together　with　impurity　of　Fe2PO5.　After　the　scCO(2)　treatment,　the　impurity　phase　was　removed,　and　the　aggregated　platelets　were　broken　into　separate　rhombus　plates　in　size　of　about　3-5　mu　m,　along　with　the　formation　of　flowerlike　balls　of　about　10-20　mu　m.　On　the　other　hand,　H2　had　the　main　morphology　of　platelets　agglomerated　in　random　directions　in　size　of　about　5　mu　m　and　covered　by　materials　of　glassy　state.　After　the　scCO(2)　measurement,　the　morphology　was　greatly　changed　and　cubic　particles　of　1　and　2　mu　m　were　formed,　together　with　the　better-shaped　and　separately　distributed　platelets　of　1　and　2　mu　m.　Therefore,　by　optimizing　the　experimental　parameters　in　both　the　hydrothermal　synthesis　and　supercritical　carbon　dioxide　processing,　it　is　possible　to　precisely　control　the　particle　size　and　morphology　of　LiFePO4.　This　work　also　presents　the　possibility　to　control　the　particle　size　and　morphology　of　other　materials　with　a　post-treatment　by　supercritical　carbon　dioxide.