The invention discloses a modular flexible connection device allowing dynamic adjustment of the stiffness and belongs to the mechanical design technical filed. An upper top plate is fixed on an installing ring, a bearing installing frame is fixed on a lower base plate through a connecting column, and accordingly the upper top plate and the lower base plate can only rotate relative to each other to maintain the mutual distance to be fixed and accordingly the required stable connection function is achieved. The stiffness variable function is achieved through the change of the relative position of a sliding block and the tail end of a spring piece. When a wire rolling shaft rotates, the reciprocating motion of the sliding block can be ensured along with the extension and retraction of two steel wires and accordingly the relative position of the sliding block and the tail end of the spring piece can be changed. According to the modular flexible connection device allowing the dynamic adjustment of the stiffness, the stable connection and stiffness variable functions are integrated into a whole and accordingly the modular production and utilization is convenient and the industrial application and popularization is convenient and the structural design is compact, the size is small, and accordingly the installation requirements under the condition that the size is limited can be met.