Real-time and label-free surface plasmon resonance (SPR) sensing has been utilized for many applications, such as environmental monitoring, disease diagnostics and drug development. The SPR can be excited on noble metal films such as Au, Ag, Cu and Al through a prism or metallic nanostructures. Compared to the prism-coupling SPR sensors, nanostructure-based SPR sensors have many benefits, including simple measurement setup, small detection volume, and ease of multiple detections. To benefit commercial applications of those metallic nanostructures, massive fabrication of low-cost nanostructures is an important issue to be addressed. In this study, we developed a robot-assisted hot-embossing nanoimprinting technique for rapid and low-cost fabrication of nanostructures and fabricated low-cost, large-area, and highly sensitive aluminum nanostructures on A4 size plastic films. The capped aluminum nanoslit array has an extremely sharp resonance with a bandwidth only 2.7 nm in the visible light region. It achieves a figure of merit (FOM) of 150, and an intensity sensitivity of 29,345 %/RIU (refractive index unit). In addition, the sensing capabilities of the aluminum nanostructures were verified by measuring bovine serum albumin (BSA) and anti-BSA interactions. Different from the conventional nanoimprint lithography, no release agent or epoxy was required for the proposed method and the imprinting process was completed within several seconds. Such low-cost, rapid, and high-throughput fabrication of highly sensitive SPR sensors can benefit commercial applications.