The numerical simulation of kinetic processes in the negative hydrogen ion (H−) sources was carried out with reflector‐type discharge being performed under high specific power. It was shown that at lower specific power (P≤100 W/cm3) the concentration of negative hydrogen ions (NH−) is proportional to the discharge current (I), but as the specific power increases the NH−is proportional to &sqrt;I. The aforementioned circumstance leads to the H−density saturation at P≳500 W/cm3.