The hysteresis phenomenon in electron cyclotron resonance plasma has been investigated theoretically by solvingthe equations of the density and energy balance of electrons and by taking the effects of several collisions suchas ionization and recombination into account. The results show that multiple steady states in experimentalmeasurements can be characterized by considering the fact that the energy balance function has three differentreal roots in certain regions of parameters. One root represents a saddle point and other roots represent stablepoints, that is, the system is bistable. The effects of ionization and the energy transformation due to the collisionsbetween the electron and neutral gas are also discussed.