The invention discloses a portable apparatus for measuring the dielectric property of a large-test-piece elastic material in a non-linear stretching state. The portable apparatus comprises a base, the base is provided with a lower flat plate used for placing a flat plate sample, an upper flat plate used for being attached to the lower flat plate and compressing the flat plate sample is fixed on the base, and the lower flat plate is arranged in a groove arranged on the upper surface of the base and is driven to perform one-dimensional movement in the groove by a horizontal screw rod connected to one end of the lower flat plate. According to the portable apparatus, the upper surface and the lower surface of the sample are fixed via a clamp, and non-linear stretching of the sample can be realized via the movement of the clamp. The conventional measuring device can only test the performance of the sample in the non-linear stretching state or perform linear stretching of the sample by employing the conventional clamp and test the dielectric property (space charge characteristic, resistivity characteristic, and dielectric property etc.) of the sample, the apparatus provides important theoretical values for the change mechanism of the dielectric property of the research material in the stretching state or the non-linear stretching state and important engineering application values for further improvement of the design structure of cable accessories, accurate control of the stretching length can be realized via the control of the screw rod, and continuous transformation of the stretching rate of the same sample can be realized.