The invention relates to the technical field of power supply chips, and discloses an RBCOT-BUCK circuit for improving transient response and high stability. The RBCOT-BUCK circuit comprises an RBCOT internal loop and an RBCOT external output circuit, and further comprises a ripple cancellation circuit, wherein the ripple cancellation circuit is arranged in the RBCOT internal loop and used for generating a compensation ripple signal with the amplitude being identical or close to that of an output feedback voltage ripple signal of the RBCOT and the phase being opposite to that of the output feedback voltage ripple signal of the RBCOT, and an output signal of the ripple cancellation circuit is superimposed with the output feedback voltage ripple signal of the RBCOT and then connected to the RBCOT internal loop. According to the technical scheme of the invention, the compensation ripple signal is generated in the RBCOT internal loop, and the stability of the RBCOT loop is greatly improvedthrough cancelling the feedback voltage ripple; and meanwhile, the load transient response performance of the RBCOT structure is enhanced, and the mutual restriction between the transient response performance of the RBCOT and the stability of the loop is effectively eliminated. The load transient performance of the circuit is can be pushed to the limit, the design difficulty is greatly reduced, and the performance of the RBCOT structure is improved.