Abstract: In order to leach unprofitable matter of decompo sition of Low-grade barium mineral below 1000℃,The decomposition behavior and mechanism and it's change regularities of Low-grade barium mineral from Sichuan Wanyuan miaozi below 1000℃ was studied by using term experiment of decomposit ion factor,thermal analysis,X-ray diffraction analysis and kinetics compute.The optimum condition that the Low-grade barium mineral of Wanyuan miaozi was boas ted on enrichment of Ba was as show:the particle size was 40~120,the boasting temperature was 950℃,the boasting time was 2h.the decomposition rules of Low-g rade barium mineral of Wanyuan miaozi was as show:the barytocalcite、barytodolom ite、dolomite、decomposed at 720℃~815℃,The step of decomposition was control led by nuclear producing and growing process(n=1),the decomposition mechanism may be expressed as follows:-ln(1-a)=kt,The second step of decomposition at 815℃ ~1000℃ was the barytocalcite、barytodolomite、dolomite was continued decomposi tion and CaCO₃ which was the decomposing matter of dolomite and calcite were decomposed,there were a small quantity of Strontium carbonate and barium carbonate also decomposed,the decomposition process was controlled by three-dimensional diffuse(ball symmetry),the decomposition mechanism may be expressed as follows: 1-(1-a)^1/32=kt.