The invention provides an included angle and
gravity center varying mechanism for
tail fins of a bio-robotic fish. The mechanism comprises a housing, a lead screw, guide rods, a slide block, a balancing weight, racks, gears, shafts and the
tail fins, wherein the guide rods, the racks, the gears and the
tail fins are symmetrically distributed about the lead screw. According to the mechanism, the lead screw can be rotated to drive the slide block, the balancing weight and the racks to move forwards and backwards, and on that basis, included angles of the tail fins can be switched between a cruising mode and a charging mode; the balancing weight can move to automatically adjust the
gravity center of the bio-robotic fish; when the bio-robotic fish is to enter the cruising state, the lead screw can be
clockwise rotated to drive the balancing weight and the racks to move forwards, and the movement of the racks can drive the gears to rotate to enable the tail fins to backwards incline relative to a fish body, so that the
gravity center can move forwards, and as a result, the fish body can keep balance and remain stable so as to enter the cruising state; if the bio-robotic fish is to enter a charging state, the lead screw can anticlockwise rotate to drive the balancing weight and the racks to move backwards, and the movement of the racks can drive the gears to rotate to enable the tail fins to be vertical to the fish body, so that the gravity center can move backwards, and as a result, the fish body can keep balanced and remain stable so as to enter the charging state.