The　main　purpose　of　this　paper　was　to　validate　whether　the　method　using　features　of　ultrasonic　radio　frequency　signal　(URFS)　is　effective　for　non-invasive　monitoring　in　microwave　ablation.　A　total　of　15　fresh　in　vitro　porcine　livers　were　experimented.　Features　of　amplitude　integral,　energy,　sum　of　absolute　value　of　difference　(SAD)　integral,　time-shift　and　attenuation　coefficient　of　URFS　were　extracted.　Changing　rules　of　these　features　and　the　relationships　between　time-shift,　attenuation　coefficient　and　tissue　temperature　were　analyzed.　Experimental　results　showed　that　maximums　of　amplitude　integral,　energy　and　SAD　integral　occur　at　the　temperature　within　50-60°C.　In　addition,　there　was　a　linear　relationship　between　time-shift　and　tissue　temperature　within　60°C　and　the　ultrasonic　attenuation　coefficient　increased　with　the　temperature　rising.　Therefore,　features　of　URFS　can　reflect　the　change　of　tissue　property　and　may　be　used　in　the　non-invasive　monitoring　of　microwave　ablation　in　the　future.　©　2011　IEEE.