A voltage level shifter formed by single-typed transistors comprises two input terminals, two power supply terminals, a plurality of thin-film transistors, and an output terminal. Another voltage level shifter formed by single-typed transistors comprises two input terminals, an output terminal, two power supply terminals, two input units, a first thin-film transistor, a disable unit, a feedback unit, and a second thin-film transistor. The voltage level shifters are formed by single-typed TFTs. When integrating the voltage level shifters into a substrate of a TFT display, the manufacturing processes are simplified. Besides, power is saved.