Abstract: The present invention provides a laser transmitting circuit, a laser receiving circuit, a distance calculation circuit and devices thereof. The laser transmitting circuit comprises an energy storage capacitor, a laser transmitting tube, an MOS switch circuit and an MOS switch driving circuit. The laser receiving circuit comprises a laser receiving tube, a first low-noise triode, a second low-noise triode and a low-noise wideband amplifier. The distance calculation circuit comprises a singlechip, a programmable logic circuit, a clock source and an echo identification circuit. The present invention further provides a low-voltage power circuit that provides a reverse polarity protection to an external power supply without additional diode connected in reverse polarity. According to the technical solutions provided by the present invention, the measurement range and precision of a semiconductor laser rangefinder can be improved effectively.