Bio-sensing is an important application in the devices of plasmonic metamaterials. However, most of such metamaterial devices were basing on the separated metallic nano-structures and limited in the absorption effects at resonance frequencies. Here we present a novel bio-sensor basing on nanoscale complementary split ring resonators with unique function of controllable narrow band-pass. The nanostructures with unit size of 100 nm and slit width of 30 nm were fabricated by e-beam lithography and ion beam etching. And the detecting measurement result indicated that the nanostructure is sensitive to the solution of bovine serum albumin (BSA). This would pave a new way to the further application of plasmonic metamaterials in chemical/biological sensing.