In an ECR ion source many parameters are related to the heating of the electrons. The amplitude of the electric field is one of the main factors. In addition to this, many other parameters affect the production of highly charged ions inside the ECR ion source - for example microwave frequency, the strengthand configuration of the magnetic field, plasma density, neutral density and so on. Since the ionization becomes more and more difficult when the charge state increases the ionization has to be as efficient as possible. How will the gradient of the magnetic field and the microwave frequency affect the energy of the electron? The computer code to reveal information about these parameters has been developed. The simulations have shown that more efficient heating will be achieved with higher microwave frequency and with smaller gradient of the magnetic field. Lower gradient of the magnetic field is obtained, for example, by using a larger plasma chamber. It was also noticed that the heating efficiency is more dependent on the microwave frequency at high plasma density and more dependent on the gradient of the magnetic field at low plasma density
