To cope with the uncertainty of Grid environment, an ER (Evidential Reasoning) based Vague multi-QoS (Quality of Service) measuring approach is proposed. The approach utilizes Vague set to denote the QoS of users or and resources, and utilizes D-S theory based ER algorithm to integrate the layered multi-QoS into a single utility value. The calculation example proves the feasibility and validity of the approach. Further- more, the approach is applied to grid task scheduling, and a new grid task scheduling algorithm (VSFM- QoS-Guided-TS) is presented. Experimental results demonstrate that the algorithm does not only reserve the uncertainty of QoS but also reduces the scheduling makespan and improves the scheduling efficiency.