The　objective　of　this　study　is　to　explore　a　new　method　for　noninvasive　temperature　estimation　of　microwave　hyperthermia　using　ultrasonic　integrated　backscatter　(IBS).　Water　bath　heating　experiments　were　performed　to　fresh　in　vitro　porcine　liver　tissues,　and　original　ultrasonic　radiofrequency　signals　at　different　temperatures　were　collected.　IBS　at　each　temperature　was　analyzed,　and　the　correlation　model　between　IBS　and　temperature　was　built　for　temperature　estimation　in　microwave　heating　experiments.　The　correlation　model　was:　IBS　=0.062×t　+3.591.　The　correlation　model　based　temperature　estimation　for　microwave　hyperthermia　had　a　small　error　(＜5°C)　in　the　temperature　range　≤70°C,　and　a　larger　error　(＞10°C)　in　the　temperature　range　＞70°C.　Experimental　results　indicate　that:　1)　IBS　may　be　used　for　noninvasive　temperature　estimation　of　mild　hyperthermia;　2)　because　of　the　heterogeneity　of　temperature　distribution　in　microwave　hyperthermia,　it　was　difficult　to　estimate　the　temperature　accurately;　and　3)　it　may　be　a　potential　approach　for　detecting　thermal　coagulation　zones　based　on　the　difference　between　the　IBS　of　normal　and　coagulated　tissues.