The formation of the spectrum of ions leaving the Z-pinch constriction during its compression is considered in the framework of the thermal mechanism corresponding to collisional regimes at high density. This mechanism refers to the heating of all ions due to compression without consideration of the electromagnetic acceleration of any selected group of ions. It is shown that such conditions can be implemented in relatively high-density regimes in which the product of precompression density and radius is n0a0 ≫ 1024 m–3. Neutron yield is analyzed. Possible parameters of a fusion reactor based on a high-density Z-pinch are estimated and found to be extremely high in terms of today’s technology.