Abstract: Experimental study was carried out in order to study the influence of building materials with different dielectric constants on the GPS monitoring signals. The determination tests on dielectric constants were carried out on four common non-metal building materials. By selecting two non-metal materials and one metal material as research objects, a set of simulation and monitoring system for GPS multipath signals was established, and the continuously two-day-long GPS monitoring data of different materials were obtained by means of placing board, PVC sheet and ceramic tiles with different dielectric constants at different heights and distances from the antenna of the GPS receiver. The improved particle filtering algorithm is used in the GPS data post-processing. By comparison, it is shown that the multipath signals caused by the same reflecting material increase with the distances decreasing, and the extent of decrease gradually tends to be smaller under the condition of increasing the same distance. The multipath errors caused by the reflecting materials with different dielectric constants at same distance increase with the dielectric constants increasing; and the multipath errors caused by the metal materials changes dramatically, which are much bigger than those caused by non-metal materials.