Aiming at realizing the selfpowered wireless network node, this paper proposes an adaptive impedance matching scheme for thermal harvest with low power consumption based on MSP 430. In order to reduce the power consumption, micro controller MSP430 is used to output PWM wave to control the MOS switch. The scheme emulates a resistor to achieve maximum power tracking. A/D module inside MSP430 gets the circuit parameters to regulate the PWM wave using perturbobserve method. This paper designs experiment to obtain the relationship between the output power and the duty cycle of PWM wave. Then, some experiments have been done to test the working performance of the scheme under variable temperature conditions. Experiments show that the scheme proposed in this paper realizes the stable selfpower supply and improves the energy harvesting efficiency and the output electric power greatly.