Ag-Fe3O4 nanocomposites were synthesized by the redox reaction between Ag2O and Fe(OH)(2) in the absence of additional reductant at moderate temperature and atmospheric condition. The as-synthesized Ag-Fe3O4 nanocomposites are assembled into an orderly arrayed SERS substrate holding clean and reproducible properties with an applied external magnetic field. 4-mercaptobenzoic acid (4-MBA) is chosen as the probe molecule to test the enhancement factors (EF), uniformity and reproducibility of the SERS substrate. Experimental results indicate that the EF of 4-MBA on our proposed SERS substrate is up to 5.2 x 10(6) and the detection limit is down to similar to 10(-10) M. The SERS spectra of 4-MBA molecules ranging from 200 cm(-1) to 2000 cm(-1) were randomly collected from a number of positions on the substrate and six Ag-Fe3O4 nanocomposites substrates are measured with the same procedure. It is shown that the SERS substrate have the good uniformity and reproducibility with low standard deviation, indicating our proposed Ag-Fe3O4 nanocomposites with external magnetic field control abilities have potential applications in the fields of magnetic separation and SERS techniques. (C) 2014 Elsevier Inc. All rights reserved.