The demand for lithium resources continues to grow owing to the extensive application of lithium-ion batteries in the clean energy industry, and in consequence the development of lithium extraction technologies is significant. In this study, the mixed solution of H2SO4 and FeCl3 was found to have a synergistic effect on the lithium extraction from a clay lithium ore. Upon calcination at 600 °C for 60 min, followed by leaching with a mixture of 10.5 w% H2SO4 and 2 w% FeCl3 at a liquid-to-solid ratio of 5 mL/g for 90 min at 80 °C, a lithium leaching efficiency of 96.18 % was obtained, better than using individual H2SO4 and FeCl3 at higher concentrations. The TG-DTG-DSC, FTIR, BET and XRD results showed that with the increase of calcination temperature the structures of partial minerals such as kaolinite and cookeite became collapsed, amorphous, unstable and activated, which favored for the release of lithium. With the further increase of calcination temperature, the mineral structure continued to collapse and tends to be stable, making the interlayer lithium tightly fixed and difficult to be released. The XRD and SEM results indicated that the lithium extraction is an ion exchange process rather than mineral dissolution. The synergistic effect of H2SO4 and FeCl3 on the lithium extraction was attributed to the fact that the entry of Fe3+ into the interlayer of the layered structure of clay minerals not only released Li+, but also increased the interlayer spacing, conducive to the access of H+ to the interlayer, and consequently facilitated the ion exchange of H+ and Li+.