A power-assistance bicycle using a sensor having multiple magnet blocks evenly distributed in a housing, related to electric power-assistance bicycles that provide a power-assistance signal with multipoint magnetic induction. The sensor comprises: a sensing element, a power-assisted model processor, a digital-to-analog converter and an operational amplifier. The sensing element comprises a rotating disk and an annular-groove fixing disk fitted with each other, and a permanent magnetic block and the Hall element are provided in a cavity of the rotating disk and the annular-groove fixing disk. A plurality of permanent magnetic blocks that are opposite in adjacent magnetic polarities are fixedly provided on the rotating disk. The Hall element is provided on the fixing disk and in proximity to the permanent magnetic blocks. The sensor is sleeved on an exterior of a medial axis. The operational amplifier is connected with the motor controller.