Fluid dynamical interactions between liquid and a solid particle have been experimentally clarified in isotropic turbulence generated by a grid in a gravitational flow. Particles with mean diameters of 180 μm and 476 μm were loaded into the flow with Up0=0.4 m/s, 0.7 m/s and 1.5 m/s at the center point of the test section well downstream of the grid so that the turbulence was steady and locally isotropic. A laser-Doppler velocimeter capable of particle size discrimination was employed for detailed measurement of particle and liquid velocities and particle number density. The results show that particle motions become nonisotropic due to gravity. Momentum transport between particles and turbulent motion is absent due to the nonisotropic particle motion and the relative velocity between particle and fluid. The eddy diffusivity ratios between particle and fluid are well correlated by the Stokes number which is calculated from the Kolmogorov time scale at the inlet position and the particle relaxation time. It is pointed out from the results that the interaction between particle and turbulence motion at the initial point governs the particle dispersion in the grid turbulence. In the grid turbulence, overshoot phenomena do not occur, and therefore, the maximum value of the diffusivity ratio is approximately equal to unity.