The authors herein present a cost-effective and innovative method to prepare scalable SERS substrate based on a repeated grafting-casting process on polydimethylsiloxane (PDMS). With the application of magnetic nano-particles, the SERS substrate can easily form abundant nano-scaled features on the micro-scaled topologies for 'hot-spots' generation, while also exhibits magnetic property enabling the remote control which might be of great importance for real harsh conditions. Via optimizing the fabrication parameters, the Raman spectra from the SERS substrate experimentally confirms the capability with good linearity within R6G concentrations of 10 to 10 mol l. Thanks to the compactly existent 'hot-spots', the gold thin film coated SERS substrate exhibits excellent uniformity with relative standard deviation of 8.5% at 1360 cm and 11.3% at 1509 cm for R6G detection (10 mol l). The demonstrated methodology can be highly promising towards the large-scale, productive and economic SERS substrates for future use in on-site chemical analysis or bio-sensors.