A handheld constant-stiffness ring shear apparatus has a base and an annular rigid frame arranged on the base in a sleeved mode. An upper cover is buckled to the top of the rigid frame, a pressure transmission plate is fixed to the upper portion of the upper cover, and a rotary shaft is perpendicularly arranged in the center of the base. The rotary shaft penetrates through the pressure transmission plate and is fixed to the pressure transmission plate. A spanner is fixed to the top end of the rotary shaft, and a digital display instrument is embedded in the spanner. The handheld constant-stiffness ring shear apparatus is convenient to carry, easy to operate, economical and practical, and can be used for measuring the volume chance of a soil sample at a field location under the constant-stiffness condition in the shear force resisting and shearing process.
