A large-scale 3D laboratory model is constructed to simulate a karst aquifer. Three groups of experiments are conducted to study the flow exchange between matrix and conduit domains and investigate the effect of head difference, conduit size, and matrix/conduit gradients on matrix-conduit exchange. The findings of current study could be summarized as, 1) In experiments with higher matrix head, a counterintuitive head inversion, where conduit head becomes higher than matrix head, occurs when the head difference between matrix and conduit domains is small (less than 9.3 cm and 11.5 cm for the smaller 1-inch and larger 2-inch conduits, respectively). 2) Flow exchange is positively related to rescaled head difference (RSHD), a parameter combining the effect of matrix/conduit gradients and the head difference between conduit and matrix domains. 3) When the conduit has the higher hydraulic head, the flow exchange is on average 2.8 times higher than when the matrix has the higher hydraulic head. 4) Doubling the conduit size doubled the flow exchange and slightly increased the length of the head inversion.