We present a theoretical and computational model to study the ionization of the electron cyclotron resonance (ECR) microwave discharge using a quasi-three-dimensional electromagnetic particle-in-cell plus Monte Carlo collision method. The simulation code is original. The detailed information about the distribution of charged particles and electromagnetic fields are obtained. We can conclude that the electrons absorb energy from microwave near the ECR region. Many electrons and ions are created through the ionization collisions between electrons and neutrals. And the distribution of charged particles vary gradually from anisotropic to isotropic by the frequently collisions.