A Maxwell molecule interactions model by the Monte Carlo method is proposed for space plasma simulations. The model describes a collision between a minor ion with a background neutral. As a result of a Maxwell molecule collisions, the magnitude of the relative velocity is unchanged but its direction is altered. However, the velocity of the center of gravity remains the same both in magnitude and direction before and after the collision. In the simulation, pairs of particles are generated at random, the changes in the velocities due to Maxwell molecule interactions are calculated.