The existing LNG loading and unloading station tank car filling has many issues such as manual filling, difficult operation of manually pushing the connecting arm, high labor intensity, long duration, low efficiency, etc. To address these issues, this paper proposes a control method of LNG rigid pipe receiving arm with automatic docking that operates within the boundary of a pre-defined vehicle parking area. The first is to collect the displacement of each actuator in real time, and convert it into the angle and angular velocity of each rotary joint motion. In order to effectively suppress interference, prevent signal from mutation, the 1st-order lag filtering algorithm is introduced, and the filtered signalis fed back to the control system. The second is to establish the kinematics model of the receiving arm through D-H (Denavit-Hartenberg) representation. The forward and inverse kinematics analysis of the connecting arm is then carried out. The third is to plan the position and posture of the receiving arm end in real time and space and its corresponding velocity and acceleration in Cartesian rectangular coordinate space. The fourth is to establish the position and velocity dual-loop controller of the outer loop angle control and the inner loop angular velocity control. The fifth, the Matalb robot tool is used to verify the correctness of the forward kinematics solution expression and the simulation of the motion range of the connecting arm. The control effect of the double-loop and single-loop PID (Proportional-Integral-Derivative) control algorithms is simulated using a step signal. The actual test shows that the accuracy of automatic docking can reach 99%, which can save 30% docking time as compared with the manual operation, effectively improve the docking efficiency, reduce the number of operators and labor intensity. The new method can be better and widely used in tank car filling automatic docking in LNG loading and unloading stations, and definitely has value as reference and in promoting such application.