The density of energy states were obtained in a quantizing magnetic field at different temperature and for nonquadratic dispersion law. The dependence of the density of energy states on temperature in quantizing magnetic fields is studied with the nonquadratic dispersion law. The continuous spectrum of the energy density of states at low temperature is transformed into discrete Landau levels. The theory of the temperature dependence of the oscillation Shubnikov–de Haas in semiconductors with a nonparabolic dispersion law is constructed, taking into account the thermal broadening of the Landau levels. The cyclotron effective mass of the electrons is determined from the Shubnikov–de Haas data.