We report new p-type metal oxide semiconductor thin-film transistor with high field-effect hole mobility fabricated in solution process in this work. Metal oxide semiconductors have long attracted large attention as large-area electronic devices by virtue of high electrical and optical performances such as transparency, large electron mobility, good uniformity and low-temperature processability since the pioneering work of Prof. Hosono group in 2004, and their mass production has now been successfully realized in the active matrix backplane of flat-panel or flexible display. Few p-type metal oxide semiconductors with high performance, however, have been reported compared with n-type metal oxide semiconductors such as InGaZnO, InZnSnO, etc. This is mostly ascribed as the localization of valence band maximum which mainly consists of oxygen p orbitals. To enhance the dispersion of valence band, it has been theoretically proposed that the filled diffuse metal d or s orbital to hybridize with oxygen 2p orbital can be utilized and indeed it was experimentally demonstrated that Sn 5s orbital and Cu 3d orbital played such a role in SnO and CuO, respectively. But, SnO phase is very vulnerable to disproportion reaction to metallic Sn and SnO₂ which behaves as an n-type semiconductor so that the process window to realize it in electron devices was very narrow and the electrical performance in the devices such as thin-film transistor was very limited, e.g low on/off ratio. Inspired by the theoretical work of high throughput materials screening performed by the first principles calculation, we fabricated the alkali metal doped SnO thin-film with solution process and low-temperature annealing less than 400 ^oC. We found that the oxidation state of Sn in thin-films changed from +4 state (SnO₂ phase) to +2 state (SnO phase) depending on the content of alkali metal ions from x-ray photoelectron spectroscopy (XPS). Furthermore, Hall-effect measurement indicated the type conversion of the majority carrier from n-type to p-type as the content of alkali metal ion increases, in consistence with XPS results. The high hall mobility of 51 cm²/Vs was obtained at the optimal alkali-metal ion doped SnO thin film and we successfully fabricated thin-film transistors with alkali-metal ion doped SnO with a field-effect hole mobility over 7 cm²/Vs. We hope that this work will contribute to open a new era for transparent large area electronics based on oxide semiconductors with high functionalities such as complementary logic circuit.