A　large-area　periodic　array　of　regular　Ag　nanoparticle　trimers　was　fabricated.　This　array　offered　reliable　polarization-independent　surface-enhanced　Raman　spectroscopy　(SERS)　performance　for　practical　macroscopic　detection.　In　polarized　SERS　experiments　for　macroscopic　detection,　it　was　found　that,　for　any　random　incident　polarization　within　the　full　360　degrees　range,　the　periodic　array　of　regular　Ag　nanoparticle　trimers　always　outputted　an　undifferentiated　SERS　signal　with　a　stable　intensity.　Finite-difference　time-domain　simulations　showed　that　the　reliable　polarization-independent　performance　of　the　periodic　Ag　nanoparticle　array　arises　from　the　unique　structure　of　the　regular　nanotrimers.　It　was　found　that　the　polarized　SERS　characteristic　of　any　single　probe-adsorption　position　is　polarizationdependent,　but　the　structure　of　the　regular　Ag　nanoparticle　trimers　could　hybridize　the　totally　polarization-dependent　SERS　signals　from　every　single　probe-adsorption　position　to　form　a　polarization-independent　SERS　signal.　This　periodic　array　of　regular　Ag　nanoparticle　trimers　was　thus　shown　to　be　a　reliable　and　reproducible　SERS　substrate　with　the　potential　to　allow　convenient　and　flexible　macroscopic　SERS　detection　outside　of　the　laboratory　setting　without　requiring　an　optimal　incident　polarization.