Abstract: In recent years, because high water content and water channeling have become major problems in oilfield, pre-crosslinked particle gel(PPG) technology has become one of high-speed growing deep flooding technology. Weighing method was used to study the expansion properties of PPG. The effects of PPG preparation conditions and external environmental factors on expansion property of particles were analyzed completely. The experimental results show that, at the PPG preparation conditions, as the increase of mass fraction of acrylamide and crosslinking agent, and the decrease of mass fraction of the initiator, the particle expansion ratio decreases gradually; as the increase of surfactant and ionic content, the particle expansion ratio decreases; as the increase of temperature and pH value, the expansion ratio of the particles also increase.