Aiming at the transient overvoltage at the sending end system caused by commutation failure in LCC-HVDC transmission systems for renewable energy integration, a risk assessment method for transient overvoltage at the sending end is proposed. First, the dynamic interaction mechanism between the renewable energy and DC transmission system under commutation failure is analyzed, and the transient voltage amplitude variation characteristics at the sending end under such interaction are studied. Then, a transient overvoltage assessment method considering the coupling effect of DC line dynamics and multi-control links is proposed. Furthermore, a critical short circuit ratio is introduced to quantify the transient overvoltage safety margin at the sending end, enabling the risk assessment of the transient overvoltage and analyzing the influence of the coupling effect of the AC-DC system on the transient overvoltage assessment. Finally, using a PSCAD simulation model of a renewable energy transmission system using LCC-HVDC, the accuracy and effectiveness of the transient overvoltage risk assessment method are verified.