Abstract: As a comprehensive characteristics of the mechanical strength of soil,the cone index (CI) has been widely used After reviewing the history and the evolution of the soil penetrometer,an automatic soil penetrometer which powered by a small reversible electric motor and controlled by a computer was developed The computerized system could control the whole process of soil penetration,including the automatic starting of the soil penetrometer,the automatic recording and an alysing of the test results and the automatic stopping when the soil penetrometer reaches the preset depth or the resistance exceeds the preset limit The test results showed that this automatic soil penetrometer could be used in indoor soil bins or field situations