The increasing popularity of video delivery among mobile users makes the problem of explosive traffic growth becoming more and more serious for traditional wireless networks, and video transmission based on D2D (device-to-device) communication through MONs (mobile opportunistic networks) is regarded as an ideal way to resolve this issue. However, data transmission in MONs is mainly through the two ways: data replication and data forwarding. Thus, to achieve high delivery ratio and low delivery delay, data replication is usually excessively exploited, and the large number of redundant replicas will not only consume large amount of nodal resource but also greatly increase the overload of networks. For video transmission, this issue becomes more severe for its volume and continuity. Thus, this study proposes a novel routing scheme for video data transmission in MONs, based on multi-player cooperative game, which can maximize the quality of reconstructed video data while minimizing the overhead of nodal and network resources. Specifically, the marginal gain model is first constructed for video delivery quality, and then the video data transmission is modeled among multiple encounters as a multi-player cooperative game. Under the guidance of Nash equilibrium theory, the video data carried by these encountering nodes is adaptively and optimally re-assigned among them. Extensive simulations based on real-life mobility traces and synthetic traces have validated the effectiveness of the proposed routing algorithm.