Multi-spinning higher dimensional Kerr-AdS black holes admit the stable small-large black hole phase transition of van der Waals type. In this paper, we study the exact critical phenomena and phase structure in five-dimensional spacetime. First, we examine the thermodynamic laws in the reduced parameter space and find that they are quite different from the conventional thermodynamic laws. Then based on the reduced laws, the phase structure in different parameter spaces is investigated. The stable and metastable black hole phases are clearly displayed. We present a highly accurate fitting formula for the coexistence curve of small and large black hole phases. Using this fitting formula, we examine the critical exponents when the black hole system approaches the critical point along the coexistence curve. Moreover, employing the dimensional analysis and symmetry analysis, we also give a numerical study of the critical point for the unequal spinning black holes.These results are very useful on further understanding the microstructure of the multi-spinning black holes in higher dimensional spacetime.where d is the number of spacetime dimensions and l is the AdS radius. Adopting such an interpretation, the P -v criticality was first examined in detail in Ref. [22]. The result shows that the P -v criticality, phase transition, and critical exponents are extremely similar to that of the VdW fluid. Subsequently, this study was extended to other AdS black holes, see and references therein. Remarkably, besides the phase transition of VdW type, some rich critical phenomena and phase transitions, such as the reentrant phase transition, triple point, isolated critical point, and λ-line phase transition were observed [35][36][37][38][39][40][41][42][43][44][45][46]. These investigations not only give us new insight into the black hole thermodynamics, but also enhance our understanding on the cosmological constant.Among the different AdS black holes, the rotating ones are more attractive. In a d =4 dimensional spacetime, a rotating Kerr AdS black hole demonstrates a small-large black hole phase transition of VdW type [23]. And when the dimension of the spacetime increases, some novel phase transitions of great interesting occur. For d ≥ 6, besides the small-large black hole phase transition, the singly spinning Kerr AdS black hole also yields a reentrant phase transitions [35]. In this case, the black hole can have a phase transition from a large black hole phase to a small one, and then back to the large black hole phase with the increase of the temperature or pressure. One of the phase transitions is first-order while another is zero-order. Moreover, for a six-dimensional multi-spinning Kerr AdS black hole, a triple point emerges in the phase diagram, which is very similar to the solid/liquid/gas phase transition of water [36]. Nevertheless, the analytic or exact study of the phase transition for the rotating Kerr AdS black hole is very difficult. The reason is that, different from the charged AdS black hole case, the entrop...