To address the transient voltage stability and inter-regional power transmission fluctuations caused by the integration of distributed renewable energy into distribution networks, a distributed synchronous condenser optimal allocation method considering transient processes is proposed. First, based on the transient voltage safety ride-through standards for renewable energy, the transient voltage fluctuations and power transmission deviations of grid-connected buses under different operating conditions are analyzed, and a time-section-based transient voltage safety evaluation index is proposed. Second, an index for improving the transient voltage safety level is established, which is used to determine the installation locations of distributed synchronous condensers. On this basis, the objective function and constraints for synchronous condenser capacity allocation are formulated, and the optimization problem is solved using the Beetle Swarm Optimization (BSO) algorithm. Finally, the rationality of the distributed synchronous condenser installation locations and capacity optimization is verified through an improved IEEE 33-bus system. Simulation results demonstrate that after the optimal allocation of distributed synchronous condensers, the voltage of renewable energy buses in the distribution network meets the specified transient voltage safety ride-through standards, and the power transmission deviation is significantly reduced, validating the correctness of the conclusions and the effectiveness of the proposed method.