Through improvement of Hall probe cryogenic calibration system, a cryogenic remanence measurement system(CRMS) for chunk permanent magnet was built. With a rectangular NdFeB(N50M) permanent magnet (its size is 40 mm×40 mm×10 mm) as example, cryogenic remanence measurement technology for chunk permanent magnet was studied. Results show that main factors affecting cryogenic remanence measurement reliability are Hall probe cryogenic calibration, Hall probe location, temperature drift, and thermal expansion of the material and so on. If the same methods are used for measurement, then the cryogenic remanence measurement repeatability of a permanent magnet is less than 0.1%. The experimental study creates conditions for measurements and research of cryogenic remanence of chunk permanent magnet of high-precision permanent magnet devices, such as cryogenic undulators.