Abstract: Through analyzing the advantages and shortages of two replication coherence protocols（aggressive-copy and lazy-copy） in data grids，this paper presents an improved replication coherence architecture and a novel lazy_agg-copy algorithm.Lazy_agg-copy algorithm updates replicas randomly in multilayer architecture.Three algorithms which are Lazy-copy algorithm，aggressive-copy algorithm and lazy_agg-copy algorithm are simulated by a simulator-OptorSim.Simulation results show that lazy_agg-copy algorithm can find better balance in real-time，network load and bandwidth.