The utility model discloses an inside-the-winding partial discharge positioning device applicable to ultra-high-voltage converter transformers. According to a data flow connection sequence, the device sequentially comprises a DFB laser, an optical fiber polarizer integrated module, a single-phase three-column parallel-connection transmission circuit, an optical fiber analyzer integrated module, a PIN photoelectric detector and processing module, a 16-channel partial discharge synchronous detection system, and an ultra-high-voltage converter transformer inside-the-winding partial discharge positioning system. 16 optical fiber current sensing units are arranged in the single-phase three-column parallel-connection transmission circuit to acquire 1-16 channels of to-be-detected pulse current signals, the to-be-detected pulse current signals are transmitted to the 16-channel partial discharge synchronous detection system through a coaxial shielding cable, and a result obtained through preliminary analysis is transmitted to the ultra-high-voltage converter transformer inside-the-winding partial discharge positioning system. Identification of interference signals and positioning of multiple-column parallel-connection network-side and valve-side discharge sources in field partial discharge test of converter transformers are realized.