In this paper, a new experimental technique is presented to. study the solvent mass transfer in heavy oil and the resultant oilswelling effect by applying dynamic pendant drop volume analysis (DPDVA). In the experiment, a pendant drop of heavy oil is formed inside a visual high-pressure cell, which is initially filled with a solvent (e.g. propane). As the solvent gradually dissolves into heavy oil, the volume of the pendant oil drop keeps increasing due to the oil-swelling effect. The sequential digital images of the dynamic pendant oil drop are acquired and analyzed to determine its volumes at different times. Theoretically, a previously formulated mathematical model is applied to describe, the solvent mass transfer in heavy oil and the oil-swelling effect. The diffusion coefficient of the solvent in heavy oil and the oilswelling factor are determined by finding the best fit of the theoretically predicted volumes of the dynamic pendant oil drop to the experimentally measured data. Experimental tests are conducted for the heavy oil-propane system at constant pressures of P = 0.4 - 0.9 MPa and a constant temperature of T = 23.9 degrees C. It is found that both the diffusion coefficient and the oil-swelling factor of the heavy oil-propane system increase with pressure. The major advantage of this new technique is that simultaneous measurements of the solvent diffusivity in heavy oil and the oil-, swelling factor can be completed within two hours at the pre-specified constant pressure and temperature.