02-31U

The method of calculation of partition function of the lattice model for the magnet in the external field near critical point (CP) is proposed. The recurrence relations and their explicit solution near the critical point are founded. It is shown, that dependence on temperature of thermodynamic functions near CP, when the field value come down to zero, is in the good agreement with previous results, which were obtained by the collective variable method. The phase transition temperature (when h=0) is calculated and dependence on parameters of interaction potential is founded.