Warm dense hydrogen is investigated by ab initio molecular dynamics simulations in the region of fluid–fluid phase transition. The method of getting adjacent metastable states is developed. The metastable states are successfully obtained in the region of densities from 0.920 to 0.970 g/cm3 and pressures from 1850 kbar to 2150 kbar along an example of 1000K isotherm. The states have similar pair correlation function as equilibrium ones before the transition. The existence of metastable states provides possible physical reasons of the remarkable differences between phase transition parameters obtained by three experimental groups.