The utility model relates to a test connecting device used to connect a notebook computer and a PCM communication device, and particularly relates to a USB conversion 232 test serial port. The USB conversion 232 test serial port comprises a housing, a USB/232 interface sub port is disposed in the housing, a USB spigot extends out of the housing, a 232 interface female port is plugged into a 232 interface sub port of the USB/232 interface sub port , a second pin head, a third pin head and a fifth pin head of the 232 interface female port are respectively connected with one end of an RX signal line, one end of a TX signal line and one end of a GND signal line, the other end of the RX signal line and the other end of the TX signal line are connected with a positive plug, the other end of the GND signal line is connected with a negative plug, and the positive plug and the negative plug both extend out of the housing. When the USB conversion 232 test serial port is used, the USB spigot is plugged into the notebook computer, the positive plug is plugged into a test positive jack of the PCM communication device, and the negative plug is plugged into a test negative plug of the PCM communication device, so test wiring of the PCM communication device is completed; and the test serial port provides great convenience for on-site testing of the PCM communication device, and working efficiency is improved.