Biomimetic robotic fish is a new type of underwater robot with many superior characteristics such as high movement speed, high motion efficiency, high energy efficiency, and so on. However, the traditional kinematic model for biomimetic robotic fish has many shortcomings which limit their movement speed, such as the rigid shakes of the fish’s head when it swims, which is caused by neglecting the influences of manufacturing process on the model. In order to mitigate the rigid headshaking, a revised kinematic model is proposed by introducing an offset of the joints rotation center. The proposed kinematic equations are well simulated in a MATLAB environment, and the numerical results illustrate the advantage of the new kinematic model. Finally, experimental results generated from a three-joint biomimetic robotic fish with the proposed model show that the fish’s head shaking is effectively restrained, and therefore the swimming speed is significantly improved.