In order to study the interaction process of source rock and fissure fluid and their mechanism, the creation of organic acid, and its impact factors, the simulation experiment result of the interaction between the source rockfluid was conducted. The experimental results show that the quantity of organic acid brought by type Ⅱ kerogen is more than that of type Ⅰ kerogen. Rising of temperature is advantageous to engender organic acid; however, the mineral of water has little influence on creation of organic acid. The pH value has great influence over cause of organic acid: neutral and basic is more advantageous to the formation of organic acid than the acid condition. The formation of organic acid speeds dissolution of minerals in source rock, and the influence of the organic acid dissolving carbonate mineral influence is most obvious. The formation of the acetic acid also favors dissolution of carbonate mineral. Oxalic acid is disadvantageous to the dissolution of carbonate mineral. Temperature influences greatly on source rock and its mineral compositions, for source rock is rich in carbonate, the quantity of dissolution of Ca, Mg, Na in water appears inverse correlation with temperature. Regardless of what content of carbonate is, the Si content in the solution will be risen with increasing temperature. The acid solution has a strong ability to dissolve source rock. No matter original solution is acid or basic, the reaction finally tends to be weak basic. The salinity of fluid has big influence on the dissolution of Mg, with low salinity of fluid favorable to the dissolution of Mg.