This paper presents a low-power 4.224GS/s sampler in 0.13-µm CMOS for IR-UWB receiver. In this design, equivalent sampling technique is introduced to multiply the sampling rate and offset cancellation technique is applied to achieve high resolution. The offset cancellation technique does not require any pre-amplifier and quiescent current. Moreover, the comparator core in the sampler only requires one phase clock while conventional two phase clocks are needed. The total power of sampler is only 2.4mW with active area of 0.4mm².