Based on the hydrodynamic dispersion theory, one-dimensional sand column diffusion experiments were carried out in laboratory. The core samples of phreatic aquifer media were collected in the refinery site and waste dumps site of Ningxia petrochemical branch company of China petroleum with five samples in each site. The NaCl solution was used as a tracer in the experiments and the analytical solution to the contaminant transport model of half infinite aquifer was used in the calculation of the dispersion parameters in porous media of saturated fine sand. The source of errors in the determination of diffusion parameters was also discussed. The study results have shown that the dispersivity determined by the experiments is close to each other in the waste dumps site and the refinery site. The model error imposes the most influence on the accuracy of dispersion parameter. Furthermore, field dispersion tests in large scale should be required to fully understand the dispersion characteristics of aquifer media in the Yinchuan Plain.