The invention relates to a test device and test method for detecting stress of a cable terminal of a ring main unit. The device comprises a mounting support, mounting sleeves, a cable fixing base, force measurement mechanisms and tensile force devices, wherein a sleeve mounting plate is arranged on the mounting support; mounting ports are formed in the sleeve mounting plate; the mounting sleeves are arranged in the mounting ports and used for connecting the cable terminal of a to-be-tested ring main unit cable; the cable fixing base is arranged on the sleeve mounting plate and used for fixing the to-be-tested ring main unit cable; the tensile force devices are connected with the mounting sleeves; the force measurement mechanisms are used for measuring tensile force applied by the tensile force devices on the mounting sleeves. The test device for detecting stress of the cable terminal of the ring main unit can be used for testing and analyzing the stress of the cable terminal of the ring main unit so as to provide data support for mounting of the ring main unit cable and prevent the adverse phenomenon that the electrical performance of the cable terminal is reduced due to electric field insulation breakdown.