The invention relates to a single pipe loading and unloading arm for a low-temperature ship. The single pipe loading and unloading arm comprises a supporting structure, a pipe system, a hydraulic drive system, a maintenance platform, a nitrogen gas blowing and sweeping system, an emergency escaping system, a hydraulic substation, an upper rope pulley, a steel wire rope and a lower rope wheel; the steel wire rope is arranged between the upper rope wheel and the lower rope wheel, the maintenance platform is arranged on the upper portion of the loading and unloading arm, the nitrogen gas blowing, sweeping and distributing system is arranged near an inlet flange of the loading and unloading arm, and the hydraulic substation is arranged on the side face of a stand column. The pipe system comprises a stand column pipe, an inner arm pipe and an outer arm pipe, the upper end and the lower end of the stand column pipe are constrained with a shaft, and it is guaranteed that the stand column pipe stretches out and contracts back freely in the axial direction and rotates freely in the axial direction; one end of the inner arm pipe is constrained with a hinge, and the other end of the inner arm pipe is constrained with a plane; one end of the outer arm pipe is constrained with a hinge, and the other end of the outer arm pipe is constrained with a plane. By means of the single pipe loading and unloading arm, the pipe system can stretch and contract freely under an environmental temperature as well as an ultra-low temperature working condition, and thus internal stress generated by temperature deformation is eliminated.