A device for detecting the connection state of voltage transformers during a secondary voltage-drop test comprises high-brightness low-current colorized LEDs, a normally-open three-contact button and current-limiting resistors. The three high-brightness low-current colorized LEDs are respectively connected in series with the current-limiting resistors and then are respectively connected in parallel between Ua and N, Ub and N, and Uc and N; when being pressed down, the normally-open three-contact button is conducted, when being in a normal state, the normally-open three-contact button is in an open circuit state. When wiring is finished and the secondary connection state of the voltage transformers needs to be detected, the connection state button is pressed down, the yellow, green and red LEDs are observed by eyes, if one LED in one color is bright, the secondary connection state of the corresponding phase voltage transformer is normal; conversely, the secondary connection of the corresponding phase voltage transformer is in an access failure state, and the secondary connection of the corresponding phase voltage transformer needs to be adjusted. The device for detecting the connection state of the secondary voltage-drop test of the voltage transformers is simple in structure and is practical, and the connection state of the voltage transformers during a secondary voltage-drop test can be intuitively known.