The invention discloses a system for automatically measuring a wire diameter of a copper wire. The system comprises a copper wire diameter measuring instrument; the copper wire diameter measuring instrument is provided with a diameter measuring groove; a diameter measuring device further comprises a supporting frame; the supporting frame comprises two supporting seats and a transverse arm connected between the two supporting seats; slide rails are connected between the two supporting seats; the diameter measuring device further comprises a slide block capable of sliding on the slide rail; the copper wire diameter measuring instrument is fixed on the slide block; and a copper wire limiting wheel is arranged in the diameter measuring groove of the copper wire diameter measuring instrument. With the adoption of the structure above, the system has the following advantages that 1, measurement is accurate and the copper wire is prevented from being broken in a measurement process; and 2, automatic diameter measurement of the copper wire is realized and the working efficiency is greatly improved; the two slide rails are arranged and the slide block slides on the slide rails; and the two slide rails have a very good supporting effect and stable sliding is guaranteed.