The invention discloses a novel impeller of a turbine flow sensor, which includes an impeller shaft (7), vanes (8) and an auxiliary hub (9), wherein each vane (8) is a polygonal vane formed by cutting a triangle from any position of the rectangle of the prior art from the middle area of one longitudinal and vertical edge to the upper edge of the rectangle. The novel impeller structure can obtain relatively bigger driving torque, so as to improve the meter factor of the lower-capacity point, reduce the linearity error of the meter, and improve the performance of the meter within the whole measuring range.