Abstract: This paper introduces the elementary principle of the high density resistivity imaging method which springs up in the field of hydrology, engineering and environmental geophysical prospecting in recent year. According to the characteristics of the diseases of the railway bed, the study and application of the high density resistivity imaging technique have been carried out and a new measurement scheme and data processing-image software system are developed. By comparing the results of the finite element numerical simulation to image formation and the field measure of the typical diseases of railway bed, it shows that the new technique is accurate, effective and convenient for detecting diseases of railway bed.