Focusing on the multifarious and time-consuming optimization process of traditional helper thread parameter value enumeration method, a real-time online helper thread prefetching quality assessment method was proposed. First, the help thread prefetching Quality of Service (QoS) target was defined. Second, the dynamic evaluation index of helper thread prefetching quality was analyzed, as well the helper thread prefetching QoS model. Finally, a dynamic and adaptive helper thread prefetching adjustment algorithm was presented. The algorithm was based on phase behavior and dynamic prefetching benefit information to determine the suitable degree of parameter values, and whether to need feedback optimization, so as to realize the adaptive adjustment and control of helper thread prefetching. By applying the adaptive prefeching algorithm, the speed up of Mst's hotspot module was 1.496. The experimental results show that the proposed adaptive prefetching evaluation method can control parameter values adaptively according to the dynamic phase behavior and prefetching benefit information.