In order to integrate the massive distributed resources to accomplish the complex engineering applications cooperatively, workflow scheduling is an important aspect. However, as the available computing power of Grid resources is changing dynamically, static scheduling scheme will lead to low performance in real Grid environment. Therefore, the rescheduling mechanism should be taken into consideration. Although a few relevant mechanisms have been proposed in recent year, as they do not consider the essence of dynamic feature and the relevant algorithms are too simple, they can not obtain a good enough result yet. To address these problems, a load-aware based adaptive rescheduling mechanism for DAG application called LAR is proposed. Therein, during application running, the load exception will be detected and the execution state of application will be judged to decide whether the rescheduling process should be triggered. And in rescheduling stage, an effective rescheduling algorithm which utilizes the latest prediction information is present. The simulation results show that our mechanism can outperform the relevant algorithms in NRSL, and can effectively solve the performance decreasing problem in real Grid environment.