Abstract: The construction of economic operation region（EOR） is the first step to realize automatic cruise function for bulk power grid dispatching. EOR is defined as the set of all optimal security-constrained day-ahead generation and transmission schedules with various preferences for dispatching objectives. Then, this paper develops a integrated multi-objective model of day-ahead generation and transmission scheduling for inter-regional interconnected bulk power grid via high voltage direct current（HVDC） tieline, to minimize power generation cost, carbon emission and pollutant emission. The multi-objective optimization problem is transformed into a series of single-objective optimization problems by using the normal boundary intersection（NBI） method. And a decomposition-coordination model for sending and receiving power grids based on synchronous alternating direction method of multipliers（SADMM） is constructed for each single-objective optimization problem to realize distributed solution. Finally, a uniformly distributed Pareto frontier is obtained, which is the EOR. Modified from two IEEE 39-bus systems, a test model of a two-area interconnected system via HVDC tie-line is built. The simulation verifies the effectiveness of the proposed method.