Using Bathe model,the ionization and explosion process of argon clusters in intense femtosecond laser pulses(100 fs,10¹⁶ W/cm²) has been studied. The results show that the average energy of argonions is proportional to the square of initial radius of the cluster for small clusters,and the explosion mechanism is typical Coulomb explosion. With increasing cluster size,the average energy of argon ions increases slowly and gets saturated gradually beyond a critical cluster size. The simulation results are in good agreement with experimental results.