Comparing with traditional pulse width modulation technique, the transient performances of the high step-up DC/DC converters can be significantly improved by one-cycle control (OCC) technique, which is an appropriate control strategy for interface converters directly connecting the renewable energies to the DC microgrid. However, the suitability of OCC for these converters is rarely studied. One-cycle controllability of the high step-up DC/DC Boost converter with coupled inductor is studied with theoretical researches and experimental verifications. First, with the analysis on the operating modes of the converter, its periodic switched linear system model and the criterion for OCC are established. Furthermore, one-cycle controllability of the converter is calculated in detail. Final, a prototype of the high step-up converter from 48 to 380 V is prepared. Experimental results indicate that the disturbances in the input of the high step-up converter can be depressed within only one switching cycle. Ideal dynamic characteristic for the converter under disturbance in the output is also achieved. Results of this paper are meaningful for investigations on the transient characteristics of high step-up DC/DC converters applied to DC microgrid.