In　this　study,　the　impact　of　expanded　perlite　(EP)　and　expanded　vermiculite　(EV)　on　the　refractory　properties　of　magnesium　potassium　phosphate　cement　(MKPC)-based　fire-resistant　materials　were　investigated.　The　physical　and　mechanical　properties　of　MKPC　paste　were　tested,　and　its　fire　retardancy　properties　were　studied　in　detail.　The　results　indicate　that　the　incorporation　of　EP　or　EV　to　MKPC-based　refractories　brings　a　notable　improvement　in　the　fire　resistance　and　makes　a　reduction　in　the　apparent　density.　However,　compared　with　EV-MKPC,　the　porosity　of　EP-MKPC　is　larger　and　its　moisture　content　is　higher,　so　the　thermal　insulation　performance　of　EP-MKPC　is　better　than　that　of　EV-MKPC　at　the　same　content.