The transition to 450 mm wafer manufacturing has already become a development trend for the semiconductor industry. To handle the larger wafer size, the conveyor-based automated material handling system (AMHS) is considered as the next-generation transportation. However, there is not any effective method for handling prioritized lots for 450 mm conveyor-based AMHS. This study developed an effective dispatching method named the “conveyor preemptive dispatching” (CPD) method for conveyor-based AMHS to minimize the average variable time of hot lots with the minimum impact to the transport of normal lots. Experiment results revealed that the CPD demonstrates better performance than the existing method. The CPD method reduced the average variable time by 59 % (from 14.572 to 5.904 s) for hot lots and 31 % (from 3962.394 to 2741.889 s) for normal lots. It expedites the movement of lots and significantly reduces lot average variable time and will effectively enhance the throughput of lots transportation.