A new measurement system has been developed for detecting frequency dependence of low-field alternating current (AC) magnetic susceptibility in natural samples.Instead of employing intricate AC bridge circuits, this system configuration is simple and consists of a set of primary, secondary (pick-up), and compensation coils, a function generator, and a two-phase lock-in amplifier.This system can measure both in-phase and out-of-phase components of AC susceptibility.The operating frequency can be chosen at any value between 1 Hz and 2.5 kHz, and the AC magnetic field intensity is changeable up to 1 kA·m-1.The resolution for the entire frequency range is almost the same as that of the Bartington Instruments susceptometer.Preliminary measurements were made on natural materials, including Chinese loess and paleosol samples, which indicate stronger frequency dependence for the paleosol than for the loess over the entire frequency range.This result suggests that the frequency dependence spectrum over wide band of frequencies can be useful, especially in environmental magnetism, as a new rock magnetic property to estimate the grain-size distribution of superparamagnedc particles and further to quandfy the degree of pedogenesis of eolian deposits.