Abstract: A double-sensor optical fiber probe was used to measure the radial distribution of interfacial parameters including local void fraction, local Sauter bubble diameter and local interfacial area concentration of subcooled boiling flow in circular tube under rolling condition. By coupling analysis of experimental and numerical results, the influence mechanism of phase distribution in subcooled boiling under transient force field was obtained. The results show that the magnitude of radial part of buoyancy force, lift force, turbulent dispersion force, and wall lubrication force is about 10³ N/m³, and the additional transient force is 2.3 magnitude less than other forces. The phase distribution of subcooled boiling flow under rolling condition depends on the balance for periodical radical forces including lift force, turbulent dispersion force, wall lubrication force and radial part of buoyancy force.