Hole subbands and optical transitions of superlattices in magnetic field are calculated on the basis of the Luttinger-Kohn effective mass theory. The method of calculation is described in detail, and the dependences of Landau energy levels on magnetic fields and well widths are presented. It is found that when magnetic field or well width increases the intermixing of heavy and light holes becomes obvious, only the three lowest states still keep their original characters of heavy holes. It is also found that the third light hole subband is necessary for the convergence of solutions. The magnetic-optical transition probabilities and the effective masses of cyclotron resonance are discussed.