In this paper we proposed a fully-parallel irregular LDPC decoder which uses only registers to store the temporary intrinsic messages. Our decoder adopts a simplified min-sum algorithm to reduce the hardware implementation complexity and area, and due to the factor modification we achieve a negligible performance loss compared with the general min-sum algorithm. Considering reducing the power consumption, we also propose a power-saved strategy according to which the message evolution will halt as the parity-check condition is satisfied. This strategy will save us higher than 50% power under good channel condition. The synthesis result in 0.18μm CMOS technology shows our decoder for (648,540) irregular LDPC code achieves high throughput (1 Gbps) with 9.0ns latency.