Abstract: HVDC transmission has become the main canal of the cross-regional accommodation of new energy, but the transient overvoltage at the sending end in a DC fault may cause the wind turbines to trip off, posing serious threats to the safe and stable operation of the system. In this regard, based on the transient overvoltage influencing factors, the short-circuit ratio is used as the voltage support strength of the sending end system. The relationship between the output of the thermal power units plus the new energy units at the feeding end and the short-circuit current of the converter station is derived through the Thevenin theorem and the superposition theorem, then the computation method of the short circuit ratio(SCR) under different operational scenarios is presented. Then the short-circuit ratio constraint corresponding to the voltage support strength is determined by the off-grid threshold of the new energy units. Aiming at the new energy cross-regional transmission system with energy storage, the minimum operating and curtailing costs of the system are taken as the goal. Considering the voltage support capability at the sending end power grid, a collaborative dispatching optimization operation model is established considering the constraints of the short-circuit ratio at the sending terminal and the HVDC transmission, and the model is solved by the inside point method. Finally, adopting the 28-node system and the 236-bus system in Zone 2, respectively, the results verify that the established model is able to elicit the generator set output plan and HVDC transmission plan curve by comprehensively considering the system economy and stability.