Energy use is currently an important issue in mobile embedded systems, and this will be continue in the future because of battery problems. We focused on a Dynamic Voltage Frequency Scaling (DVFS) algorithm to save as much energy as possible, and investigated the correlation of operations between memory and CPU. We introduce an Operational Intensity (OI)-based DVFS algorithm to follow the optimal frequency to conserve energy in embedded systems. Our proposed method was verified using FPMark of EEMBC, and conserved energy up to 17% in a memory-bound application.