Disclosed are a flexible surgical instrument system and a control method for the system under constraint of motion, comprising a flexible surgical instrument system composed of a mechanical arm with multiple degrees of freedom (101), a flexible surgical instrument (102), a remote control device (201) and a control computer (202). The method comprises: obtaining a target posture (302) of a surgical actuator (107) according to a status signal (301) from the remote control device (201)； obtaining a current posture (305) of the surgical actuator (107) according to a joint position value (303) of the mechanical arm with multiple degrees of freedom (101) and a structural segment turning angle value (304) of the flexible surgical instrument (102)； obtaining an expected speed (306) of the surgical actuator (107) according to the target posture (302) of the surgical actuator (107) and the current posture (305) of the surgical actuator (107)； acquiring a motion-restrained condition (309) applied to an outer sleeve (105) by sheaths (103, 108), and obtaining a joint speed (311) of the mechanical arm with multiple degrees of freedom (101) and a structural segment turning speed (312) of the flexible surgical instrument (102) according to the motion-restrained condition (309) and the expected speed (306) of the surgical actuator (107)； obtaining a target joint position value (313) of the mechanical arm with multiple degrees of freedom (101) and a target structural segment turning angle value (314) of the flexible surgical instrument (102), and sending same to the corresponding controller so as to drive various structural segments； and controlling the loop until the end, and repeatedly executing the actions of the above steps in cycles.L'invention concerne un système d'instrument chirurgical flexible et un procédé de commande pour le système sous restriction de mouvement, comprenant un système d'instrument chirurgical flexible composé d'un bras mécanique (101) présentant de multipl
