Taking compound soil under maize and potato rotation as the research objects, four sets of compound farmlands(compound soil) with soft rock to aeolian sandy soil were designed with their volume ratios of 0∶1 (CK), 1∶5(C1), 1∶2(C2) and 1∶1(C3). The mineralization process of organic carbon in compound soil was investigated using the alkali absorption method. The results showed that there was no statistically significant difference in soil organic carbon contents for the same compound ratio, and the organic carbon contents of the compounded soil planted with maize and potato in the current season were increased by 27.27% to 46.59% and 42.47% to 70.57% compared to that of the CK, respectively, and the differences were statistically significant (P<0.05), except for the C1 planted with maize. The rate of organic carbon mineralization in the compound soil during the incubation showed three stages of sharp decline, slow decline and plateau, all of which were greatest at the end of the incubation for C3. The cumulative mineralization of organic carbon in the compounde soil increased exponentially with the extension of incubation time, and the crop of the season and the compound ratio as well as the intercropping effect all had a significant effect on the cumulative mineralization of organic carbon, which was greater in C1 for maize cultivation and in C3 for potato cultivation. The cumulative organic carbon mineralization rates of the compounded soils varied considerably between the two crops, with lower cumulative organic carbon mineralization rates in C2 for maize and C1 for potatoes grown. The organic carbon mineralization rate constants of the compounded soils showed the opposite trend to the half turnover period, with C2 for maize and C1 for potato planted having larger half turnover periods for organic carbon mineralization. It could be seen that both the crop of the season and the compound ratio affected the organic carbon mineralization of the compound soil, and the rotation of maize and potato with the volume ratio of soft rock to aeolian sandy soil of 1∶2 was more suitable, which could be used as a production practice to help promote the ecological development of the Mu Us sandy land.