To improve the image contrast, the so-called contrast agents (CAs) are often used in magnetic resonance image (MRI). CAs are generally paramagnetic or superparamagnetic nanoparticle suspensions. To increase the applicability of low field nuclear magnetic resonance (LFNMR) or LFMRI system, CAs also have been introduced to enhance the image contrast. In this work, we synthesized the γ-Fe2O3/Au core/shell (γ-Fe2O3@Au) nanoparticle and applied it to a homemade high-Tc SQUID-based LFNMR system to study the characteristics of γ-Fe2O3@Au nanoparticle as the contrast agent for the LFNMR system. The average hydrodynamic sizes of the synthesized γ-Fe2O3@Au nanoparticles are 28.38 ± 6.26 nm in diameter. The γ-Fe2O3@Au nanoparticles exhibit a characteristic absorption peak at 536 nm from the contribution of localized surface plasmon resonance of Au shell. The spin-lattice relaxation rate, 1/T1, and the spin-spin relaxation rate, 1/T2, varied with the concentration of γ-Fe2O3@Au nanoparticle. Compared with the data measured in high field (7 Tesla), we found that the γ-Fe2O3@Au nanoparticle is a promising T1-relaxing CA for LFNMR.