Due to the popularity of LDPC (Low Density Parity Codes) in modern communication systems, there is a growing need of LDPC encoder with a faster encoding speed and more application compatibility. In this paper, an efficient QC-LDPC encoder architecture is proposed, which is suitable for both IEEE 802.16e standard and IEEE 802.11n standard. Owing to the special structure of multi-diagonal parity matrices, the inverse matrix is replaced with back substitution. Simplified RU algorithm is applied to the encoder structure, and the parallelism is determined by the row number of parity matrices in the two standards. The proposed architecture has full configurability with concern to code rate and code length. Simulation results confirm that the encoders work successfully from 1/2 rate to 5/6 rate under both two standards. To validate its feasibility, we have tested all code lengths of IEEE 802.11n standard and IEEE 806.12e standard. They all work accurately with the proposed encoder architecture, with the output throughputs ranging between 538 Mbps and 2879 Mbps.