The invention relates to a self-compaction neat cement paste rheological property testing device. The device consists of a neat cement paste truncated cone round mold, a divergence testing plate, an adjustable support, a distance sensing system, a light sensing system and a data analysis system, wherein the divergence testing plate consists of two layers of smooth glass plates; the front surface of the first layer of glass plate is provided with a truncated cone round mold positioning scale by taking the center of the testing plate as the center of circle, and the back surface is provided with scales having different diameters by taking the center of the testing plate as the center of circle; nonferrous metal circle rings are embedded onto the scales; the light sensing system is arranged below the metal circle rings; the adjustable support comprises a supporting seat, a bolt, a spring and a nut; the distance sensing system and the light sensing system are connected with the data analysis system through a dedicated data line. The self-compaction cement paste rheological property testing device has the advantages that the flowing duration of self-compaction cement paste can be tested in an intelligent, high-precision and high-efficiency manner by using the distance sensing system and the light sensing system; meanwhile, the divergence of the neat cement paste is accurately read by using the adjustable support and the concentric nonferrous metal circle rings.