A semiconductor device with a current sampler and a start-up structure, comprises first, second and third high-voltage transistors, and a resistor, wherein: a drain terminal of the first transistor is respectively connected to a drain terminal of the second transistor, a drain terminal of the third transistor and one end of the resistor; a source terminal of the first transistor is grounded, and a gate terminal of the first transistor is connected to a gate terminal of the second transistor; the other end of the resistor is connected to a gate terminal of the third transistor; wherein the resistor is wound and formed in a common voltage withstand region of the first transistor, the second transistor and the third transistor, or in a voltage withstand region of the first transistor only, or in the voltage withstand region of the third transistor only.