Abstract: By combining a Pockels cell and a Glan prism in a special way for polarization applications, the main pulse of an ultrahigh intensity laser can be greatly suppressed but the amplified spontaneous emission will not be weakened. Based on this fact, we designed a new method to measure the contrast ratio of ultraintense laser pulses with a high dynamic range on the order of nanoseconds. As a result, the measurable dynamic range of the contrast ratio was increased by three orders of magnitude, and a contrast ratio of 2.95×10-8 was obtained with this new technique.