Abstract: A basic problem of spaceflight dynamics named Gauss problem is how to determine the orbit by the information of the two positions and flight time. The problem of Lambert rendezvous is the embodiment of Gauss problem in the field of spacecraft rendezvous. This paper issues a new algorithm, which can solve the problem about loopy Lambert transfer of spacecraft. Then the result is applied to search for the orbit of Lambert transfer of spacecraft whose fuel penalty is optimal under the condition of long-time flight. The calculation results validate the correctness and robustness of the algorithm.