As an important measure for parties of the contract to protect their own interests, project claim is the core of project contract management. For claims of time delay under multi-agent and multi-event interference, it is difficult to assess the responsibility. To solve this problem, this paper presents a new analytical method based on Shapley value, and brings forward a new parameter called Correction Factor to denote the affecting degree of every interference event. On the basis of this method, project delay responsibility is allotted to each single responsible activity, and then allotted to both owner and contractor in each single responsible activity. Finally, the responsibility is reallotted to the responsible parties through Correction Factor. This method takes into account the impact of the interference event, and makes the responsibility-sharing more equitable.