We present numerical model of interstellar medium in irregular galaxies. The model includes magnetohydrodynamical dynamo driven by cosmic rays in the interstellar medium provided by random supernova explosions. Essential elements such as: vertical gravity of the disk, differential rotation and resistivity leading to magnetic reconnection are included in the model as well. We describe many models characterized by different: supernova frequency and periodic activity, resistivity, column density, shearing and rotation. We find that only high rotation enhances the efficiency of the dynamo. Other parameters influence very weak the evolution of magnetic fields in the irregular galaxy. Simulations have shown that high amount of magnetic energy flow out off the simulation region becoming an efficient source of intergalactic magnetic fields.