In order to improve a typical type of TDR (Time Domain Reflectometry) that requires soil disturbance for compaction control, we developed a Flat type TDR Probe. A laboratory experiment was conducted on two sandy soils to assess the applicability of the Flat TDR system. The reliability of measured values with the Flat TDR was evaluated by comparing the moisture content and dry density of soil with those of Purdue TDR. Based on the comparison of the values, it turns out that the flat type TDR can be used as an alternative to measure the dry density and water content of soil.