This Letter proposes a new scheme for optimizing a direct current (DC) component to enable both the frequency offset estimation and system performance improvement by controlling the IQ modulator to adjust the DC component in a photonics-assisted OFDM MMW system. Compared with the traditional method, a large DC component is used as the pilot frequency for frequency offset estimation. When a small DC component is used, the system performance is better. A 3 Gbaud 16QAM OFDM signal is delivered over 70 m wireless, enabling a 3.5 dB sensitivity improvement at the bit error rate threshold of in the E-band.