Traditional video information hiding usually modifies intraframe prediction modes，motion vectors or prediction residual coefficients for secrete message embedding． For HEVC ( High Efficiency Video Coding) standard，however， it adopts an advanced motion vector prediction ( AMVP) which uses both spatial motion vector and temporal motion vector of the adjacent block to predict the motion vector of the current block． The motion vector index is given to a prediction motion vector when it is used． Due to this new technique， this article first proposes to embed the secret information by modifying the index value． In order to guarantee the quality of the modified video， we analyze the relationship among the index value，the predicted motion vector and the motion vector residual so that we can accordingly modify the corresponding motion vector residual． This motion vector can remain unchanged after embedding． We control the capacity and bit rate change by means of a threshold． Experimental results show that our method has a larger embedded capacity and smaller bit rate increase． In particular，our method can ensure that the quality of embedded video is the same as the original video．