08-10U

The method of analytic calculations for physical characteristics of the $3D$ Ising-like model near the phase transition point is developed. Basing on the analysis of recurrent relations among coefficients, which characterize the effective block spins, the region of wave vectors for which the order parameter fluctuations are described by non-Gaussian measure density is established. The dependence of the region width on the temperature and field value is found. It allows us to find expressions for the free energy, order parameter and susceptibility of the system near the phase transition point. The crossover form of the equation of state, which can transfer into the well-known equations of state in the limit cases, is one of the results of calculations.