Control system of hybrid vehicle

A control system for controlling a hybrid transmission including a two-degree-of-freedom differential mechanism is arranged to change a target prime-mover (ENG) revolution speed of a prime mover so as to decrease an electric power output of first (MG1) and second (MG2) motor/generators when a temperature of one of the first and second motor/generators and a power device for the first and second motor/generators is higher than a predetermined temperature, wherein a target driving force of the hybrid vehicle is achieved by a demand prime-mover output generated when an output revolution speed of the hybrid transmission is kept constant and when the target prime-mover revolution speed is determined.