The invention discloses a method and a system for optimizing task processing in ETL. The method comprises: according to mutual relations among each task the ETL needs to dispatch, establishing a network graph, the network graph being marked with task execution sequence of each task; calculating execution time bucket of each task and/or specific point-in-time parameters related in the execution time, to obtain a calculation result used to mark each task time; according to a preset rule, scanning the mutual relations among each task in the network graph and the task execution sequence, to generate a first relation table; according to the calculation result, reordering the task execution sequence in the first relation table, to obtain a second relation table including a key task, according to the second relation table, optimizing dispatching of the execution processing of the key task.