Multi-core fiber has the advantages of high integration and large transmission capacity. In order to realize its connection with single-core fiber array, a self-assembled ultra-low loss multi-core fiber fan-in and fan-out(FIFO) device design and preparation method based on high-precision ceramic ferrule is proposed. Through simulation and experiments, the optimal parameters of the taper fiber, such as taper power and taper speed were determined, and a high-performance seven-core fiber FIFO device is successfully fabricated. The transmission link used in the experiment includes a pair of FIFO devices and a 5 m long seven-core fiber. The average loss of the seven channels is 0.9 dB and the average crosstalk is -52 dB. In addition, the FIFO device achieves 7×10 Gb/s error-free transmission in a seven-core fiber with a wavelength of 1550 nm and a length of 1 km, and the consistency of each channel is good.