New rotary to linear conversion mechanism named "reverse-type differential rotary to linear conversion mechanism (RDRLCM)" was invented for simultaneous achievement of large load capacity and precise displacement control, for compression test devices and press forming machines. The new mechanism was developed and incorporated as loading systems into an original biaxial compression test device, and thus, its fundamental performance was investigated. The results revealed that the loading system by the new rotary to linear conversion mechanism were able to generate compression force of about three times larger than that by a conventional feed-screw mechanism for the same input torque. In addition, the generated compressive force was maintained while the compressive motion was interrupted. These facts confirm the advantage to use RDRLCM for compression test devices as well as for press forming machines.