Abstract: To satisfy the requirements of fifth generation wireless communication in spectral efficiency (SE) and energy efficiency (EE), an energy efficient resource allocation approach for two-tiers downlink heterogeneous network operating in orthogonal frequencies is proposed, where data rate requirement per user and maximum transmit power per base station (BS) are considered. Antennas and transmission bandwidth are key factors affecting EE. By studying the antenna allocation and bandwidth allocation between massive multi-input multi-output (MIMO) BS and small BSs, the following conclusions can be drawn. For large number of antennas, transmit power can be ignored; when the ratio of bandwidth of the two tiers is given, the ratio of number of antennas of the two tiers using the maximum transmit power of massive MIMO BS or small BS can almost achieve the highest EE; when the ratio of number of antennas is given, the average total power consumption of the systems is convex in the ratio of bandwidth hence there is a global optimal ratio maximizing EE. Numeral results show that compared with the EE of heterogeneous network (HetNet) and small cell network without energy efficient resource allocation, the HetNet with the proposed resource allocation can achieve higher EE and the EE gain is significant for large number of users with high data rate requirement.