The　ternary　phase　diagram　of　methyl　methacrylate　(MMA)/acrylic　acid　(AA)/water　soap-free　microemulsion　system　was　figured　out　by　the　conventional　titration　technique,　and　the　domains　of　different　types　of　single　phase　microemulsions　were　partitioned　with　conductivity　measurement.　Based　on　the　phase　diagram,　the　influence　of　the　amount　of　initiator　(AIBN),　the　contents　of　AA　and　water　on　the　rate　of　polymerization　in　MMA/AA/H2O　soap-free　inverse　microemulsions　was　investigated.　The　results　showed　that　polymerization　rate　increased　with　increasing　amount　of　initiator　or　increasing　content　of　AA　and　there　appeared　a　peak　value　of　rate　with　increasing　content　of　water.　The　kinetic　relation　was　obtained,　which　indicated　that　AA　was　an　effective　emulsifier　to　enforce　and　hasten　polymerization　in　dispersed　droplets　at　the　same　time　with　conventional　polymerization　in　the　continuous　phase.　In　addition,　the　morphology　of　the　products　from　soap-free　microemulsion　was　observed　under　an　environment　scanning　electron　microscope　and　the　existence　of　microporous　structure　was　found.