In　order　to　make　better　use　of　the　low　ash　fusion　temperature　semi-coke,　increasing　the　coal＇s　ash　fusion　temperature　is　the　key　to　improving　the　coal　gasification　process.　In　this　paper,　through　comparing　with　the　effect　of　alumina　and　calcium　oxide　alone　on　ash　fusion　temperature　of　semi-coke,　the　synergistic　effect　of　alumina　and　calcium　oxide　on　the　coal　ash　was　studied.　The　effects　of　refractory　agent　A　(rich　in　alumina)　and　B　(rich　in　both　alumina　and　calcium　oxide)　on　the　ash　fusion　temperature　were　also　studied.　The　minerals　evolutions　during　the　ash　melting　process　before　and　after　A,　B　refractory　agents　were　added　were　studied　by　X-ray　diffractometer　(XRD)　and　ternary　phase　diagram　of　FactSage.　The　results　showed　that　adding　a　high　amount　of　Al2O3　and　a　small　amount　of　CaO　to　ash　had　a　synergistic　effect　on　increasing　the　ash　fusion　temperature.　The　formation　of　both　mullite　and　anorthite　had　the　synergy　effect　on　increasing　the　ash　fusion　temperature.　This　was　consistent　with　FactSage　results.