The invention discloses a full-automatic rotational inertia measuring system and relates to the technical field of rotational inertia measuring.The system comprises a base assembly, a table board ejecting assembly, a rotational inertia assembly, a support assembly, a rotation assembly and a table board releasing assembly, wherein the table board ejecting assembly, the rotational inertia assembly, the support assembly, the rotation assembly and the table board releasing assembly are installed on the base assembly.The support assembly is installed on the rotational inertia assembly and can rotate in the horizontal direction.The table board ejecting assembly comprises first air cylinders used for locking the support assembly and an optoelectronic switch used for measuring the swinging period of the support assembly.The table board releasing assembly comprises a second air cylinder used for driving the support assembly to rotate.The rotation assembly is connected with a rotation frame on the support assembly and drives the rotation frame to rotate by 90 degrees.A guided missile to be measured is installed on the rotation frame, the optoelectronic switch measures the swinging period before the rotation assembly where the guided missile is installed rotates by 90 degrees and the swinging period after the rotation assembly where the guided missile is installed rotates by 90 degrees so that the corresponding rotational inertia can be calculated, and using is convenient.