Aiming at the transient overvoltage problem of high proportion new energy multi direct current (DC) transmission system caused by DC blocking fault,the interaction mechanism between multiple DC lines is analyzed firstly and the multi-outfeed voltage infection factor is introduced,which reveals the fundamental reason of transient overvoltage of other sound DC near area alternating current (AC) systems caused by DC blocking. Secondly,based on the quantitative relationship between reactive power output of the synchronous condenser in different time scales and rectifier side commutation bus voltage and improved rectifier side control of DC system,the capacity of the synchronous condenser installed on the rectifier side bus is configured and the required investment capacity is reduced. Thirdly,based on the above strategy,integrating the reactive power regulation capability of the synchronous condenser and rectifier,a transient overvoltage suppression strategy with coordinated cooperation of multi DC and multi reactive power equipment is proposed. Finally,a double-circuit DC transmission system model is built in PSCAD simulation platform to verify the suppression effect of the proposed coordination strategy on transient overvoltage and the configuration effect of condenser capacity.