In this paper, we propose a partially-parallel irregular LDPC decoder for IEEE 802.11n standard targeting high throughput applications. The proposed decoder has several merits: (i) The decoder is designed based on a novel delta-value based message passing algorithm which facilitates the decoding throughput by redundant computation removal. (ii) Techniques such as binary sorting, parallel column operation, high performance pipelining are used to further speed up the message-passing procedure. The synthesis result in TSMC 0.18 CMOS technology demonstrates that for (648, 324) irregular LDPC code, our decoder can achieve 8 times increasement in throughput, reaching 418Mbps at the frequency of 200MHz.