This paper researched the Projectively lag synchronization and unknown parameters identification of hyperchaotic Lü system. Projection lag synchronization is realized between the driver and response system by adding appropriate nonlinear controller into response system and applyling Lyapunov stability method and Barbalat lemma. And the unknown parameters of hyperchaotic Lü system also can be identified. Finally, several numerical simulations were given to test and verify the correctness and feasibility of the methods proposed.