With the development of new power systems and the continuous production of new energy generation units, the southern region will form a scenario of multi regional new energy and adjacent conventional power sources jointly connected to the system. The centralized access of renewable generation often shares transmission channels with conventional power sources, which will affect the transient stability characteristics of regional systems and the transmission capacity of transmission channels, posing unprecedented challenges to the safe and stable operation and risk prevention of southern regional systems. An equivalent system model for regional renewable generation transmission system is established to deeply study the stable characteristics of regional new energy transmission. The main mechanism of the impact of renewable generation integration on the transient stability characteristics of regional systems is analyzed. A quantitative analysis is conducted on the acceleration and deceleration areas of the transient process of the regional transmission system based on the equal area rule. A coordinated optimization method for emergency control shutdown strategy is proposed to achieve the minimization of emergency control shutdown quantity and control cost for traditional and renewable generation units in the regional transmission system. Finally, based on the example of the Guangdong regional wind-thermal-combined power transmission system, the correctness of the analysis results is verified.