The invention discloses a rapid detection device and a detection method for the RS485 connection of a portable electric meter box. The device comprises a CPU processor. The CPU processor is respectively connected with a receiving/transmitting circuit, a gain control circuit, a voltage detection circuit, a control circuit and a flash disk data storage module. The receiving/transmitting circuit is respectively connected with a Symbol SE 900-series laser scanning engine and a liquid crystal display module. The gain control circuit is respectively connected with a key circuit and a clock circuit. The key circuit is connected with a keyboard operation system. The clock circuit is connected with an OSC oscillator. The voltage detection circuit is connected with a power supply circuit and a high-brightness flashlight. The control circuit is respectively connected with a serial port data conversion circuit and a buzzer. The flash disk data storage module is connected with a printing circuit. In this way, the point-to-point fast and automatic detection from an II-type concentrator to each electric energy meter is realized, and the wiring quality of an RS485 bus at a detection site is detected. The on-site meter-reading rate is improved. After the detection process, a detection report is formed to be exported or printed.