The cyclic deformation behaviors of 42CrMo steel with different heat treatments were observed by uniaxial cyclic straining and stressing tests at room temperature. The cyclic softening/ hardening features of the tempered or annealed 42CrMo steel and their effects on the uniaxial ratcheting produced in asymmetrical cyclic stressing were discussed. It is concluded that the tempered 42CrMo steel shows significantly cyclic softening feature, but the annealed one is cyclic stabilizing. Different ratcheting behaviors are also observed. For the tempered 42CrMo steel, a special tertiary ratcheting behavior is observed and the previous cyclic straining greatly accelerates the evolution of ratcheting strain in subsequent cyclic stressing. In contrast, the annealed sample presents a stabilized ratcheting with nearly constant ratcheting strain rate after certain cycles, and the previous cyclic straining slightly influences the ratcheting in subsequent cyclic stressing.