The temperature dependence of lattice constants a and c of intermetallic compund DyMn2Ge2 is measured in the temperature range 10-800K by using the X-ray method. The magnetoelastic anomaly of lattice constants a is observed at spontaneous magnetic phase transition from paramagnetic state to antiferromagnetic state. The ac magnetic susceptibility of DyMn2Ge2 is measured in the temperature range 4.2-200K. Low temperature magnetic phase transitions in DyMn2Ge2 are discussed in the molecular field approximation by taking into account of next nearest Mn-Mn interlayer exchange interaction. The temperature dependence of magnetization and magnetic curves at different temperatures of DyMn2Ge2 single crystal are calculated. Theoretical calculation shows that the observed field-induced magnetic phase transition in DyMn2Ge2 single crystal at temperature lower than 33K is the transition from ferrimagnetic state into intermediate state.