Abstract: In this paper, a cross-tier cooperation(CTC) strategy is proposed for a dense large-scale two-tier cellular network composed of macrocells and picocells, a closedform network energy-spectral efficiency(ESE) expression for a dense large-scale coordinated multipoint(CoMP)-enhanced two-tier cellular network is deduced, and then the impact of the pico base station(BS) density and the cooperation threshold on the network ESE can be quantitatively analyzed. The simulation results show that compared to the existing three different scenarios which including the scenario where non-cooperative communication method has been adopted in a two-tier cellular network, the scenario where all the base stations in the two-tier cellular network are involved in the cooperative communication, and the scenario where two nearest base stations from the user are involved in the cooperative communication in the single-layer cellular network, the proposed strategy can effectively reduce the cross-tier interference and the number of backhaul links, and improve the energy-spectral efficiency of the two-tier cellular network.