This paper proposes a significant motion vector protection (SMVP) scheme for error-resilient transmission of videos. In terms of a rate-distortion optimization model, we show how to determine the significant motion vectors (SMVs) and how much rate space should be preserved to store SMVs. The idea behind our method is to give more protection to significant data. As a result, our method can be regarded as a kind of unequal error protection mechanisms. In comparison with the conventional forward error correction (FEC) and error concealment methods, experimental results demonstrate the effectiveness of the proposed method. In particularly, our method shows its superiority under the situation of higher packet loss rates.