A microscopy based imaging technology was proposed to provide both surface plasmonic resonance (SPR) detection and surface-enhanced Raman scattering (SERS) spectral of attached molecules on a dual-mode biochip. Experimental studies were conducted to reveal that both SPR and SERS signals can be acquired from the same biochip. SPR excitation and low concentration SERS detection are successfully performed on metallic nanogap grating with periodicities of 400 or 600 nm ensuring the SPR excitation under the illumination of 633 or 785 nm irradiation, respectively. The excited SPR propagates on the metallic surface, efficiently excites dipole moment resonance at the nanogap in the grating trough, leading to extremely high local electric field built up at the nanogap and the metallic surface. Therefore, besides SPR detection, SERS evaluation can be conducted to identify the molecules attached on the biochip. The experimental results show that the SPR bulky sensitivity of the dual-mode biochip is S = 68.8°/RIU, and the surface sensitivity is S = 1.5°/(mol·L^-1). The Raman enhancement factor of the dual-mode biochip reaches up to 10⁶ and the minimum detection concentration of 10^-15 mol/L could be achieved. Due to its high-fidelity measurement of the dual-mode chip and the high precision of microscopy imaging technology, multi-channel label-free detection is expected to be widely used in biological detections. Our future work is to achieve the practical application of SPR-SERS dual-mode biological detection.