This paper presents a novel low power bandgap reference circuit, the bandgap reference adopts half a period working mechanism. The operational amplifier doesn't work during the switched capacitor network sampling. And the operational amplifier works after the charge balanced. The bandgap reference runs discontinuously. The design implements in standard 0.18um CMOS process. The simulation result shows that, the circuit consumes 19.8 uAat 3.3V. The noise of the circuit in low frequency achieves 3.9 mu V/root Hz and the temperature coefficient is 21 ppm/degrees C.