In this paper, stable Li-doped ZnO solid solution (ZnO: Li) is successfully prepared by sintering the mixture of ZnO and Li2O powders under a pressure of 5 GPa and at temperatures between 1200 ℃ and 1500 ℃. It is found that the high pressure and temperature conditions have significant effects on the electrical conductivity and the structure of the ZnO solid solution. The best p-type ZnO doping 4.5 at.% Li with a resistivity of 3.1 10-1cm, carrier concentration of 3.3 1019cm-3, and mobility of 27.7 cm/Vs is achieved at 1500 ℃. The p-type conduction formed in ZnO is due to acceptor formed by one substitutional Li atom at Zn site, which has an acceptor level of 110 meV. Furthermore, the effects of pressure on formation and electrical properties of the p-type ZnO are discussed.