A paper-based flexible sensor based on nano Ag/carbon nanotube（CNT） is prepared by ultrasonic-assisted sintering. CNT pastes are introduced into the conventional Ag NPs conductive ink to form the Ag NPs/CNT composite conductive ink. And the conductive lines are deposited on the paper substrate by 3D printing and sintering/ultrasonic-assisted sintering methods. The samples are then tested for mechanical properties and the microstructures are observed to investigate the effect of CNT and ultrasound. The results show that both ultrasonic and CNT can effectively improve the mechanical properties of flexible circuits and provide them the function of flexible sensors.