Abstract: In order to solve the problems of neglecting soil anisotropy and loading test direction in traditional in-situ soil deformation test, a design concept of in-situ test system for loess in-hole anisotropy deformation was proposed. The entire test system consists of a support system, a cutting system and a detection system, similar to the in-hole anisotropy in-situ horizontal load test, and a prototype was successfully developed. The prototype can be fixed at any depth in the borehole, and the plane is cut by the cutting system, and then the array squeeze plate is used for in-hole squeezing. The pressure and displacement data are recorded by the data acquisition device to obtain the stress-displacement relationship curve. Based on the field test, the reliability of the test system was tested. The test results show that the cutting system has good tool synchronization performance, and the cutting effect in the hole is good. The overall trend of the stress-strain curve is in line with the general compression deformation law of loess. The soil deformation modulus is compared with the mass moisture content and the static penetration strength parameters of the soil. With the change of the test depth, the deformation modulus is inversely proportional to the moisture content, and is directly proportional to the cohesion and peak cone tip resistance of the soil. This verifies that the results of the test system have good credibility.