Diopside-acmite is a pair of coexistent minerals in a solid solution which dissolves imperfectly. Sometimes they are associated with each other in meta- somatic rocks. But under what physico-chemical conditions can this pair of minerals actually occur togetherp Author has summarized the experimental data on the diopside-acmite paragenesis obtained from the modeling of the forma- tion of the Makeng iron deposit, which is undoubtedly significant for the study of the formation of this pair of minerals. Author used natural diabasa and marble as starting test materials.The expe- riments were carried out in a cold-seal high-pressure vessel with a gold lining. The experimental results show that the diopside-acmite paragenesis is formed wi- thin the range of 90% diabase and 10% marble to 50% diabase and 50% mar- ble,under the temperature of 500一650 ℃ and the pressure of 500一650℃ bar.,and in a nearly neutral medium of Xco2=0.0104一0.002 within the H20一C02 fluid. Some of the diopside-acmite solid solution produced in our tests has a per- fect crystal form, It is found that in this solid solution, the diopside is always more and the acmite less.This pair of minerals is often associated with garnet, tremolite, vesuvianite, and magnetite, etc. Because of the small ranges of tom- perature, pressure, pH of the medium solution and Xco2 for the coexistence of this pair of minerals, they seidom occur together in metasomatic rocks in nature.