The thermodynamic properties of a series of sulfonate resins with interpenetrating polymer networks (SRIPN) were studied and the ΔG0

ΔH0

ΔS0

of ion exchange reactions for SRIPN which have various degree of crosslinking and various weight ratio between two networks of beads were measured. The interrelation between the thermodynamic properties and structure of SBIPN was generalized. Through the study of the relation between water regain and equivalent fraction of the replacing ion on resin phase the concept of integral water regain (IWR) has been put forward. When SRIPN was applied to the ion elution chromatography of KCl

NaCl

CaCl2

MgCl2 mixture

the efficiency of separation was far better than that with SGSR.