In this letter, a surface plasmon resonance (SPR) biosensor is numerically investigated that used Graphene-MoS2-Au-TiO2-SiO2 hybrid structure for the detection of formalin. This developed sensor sensed the presence of formalin based on attenuated total reflection (ATR) method by observing the change of “surface plasmon resonance (SPR) angle versus the change of minimum reflectance” attributor and “the surface plasmon resonance frequency (SPRF) versus maximum transmittance” attributor. Chitosan is used as probe legend to perform the particular reaction with the formalin (formaldehyde) as target legend. Here, graphene as well as MoS2 are used as biomolecular recognition element (BRE), TiO2-SiO2 bilayer as the improvement of sensitivity and Gold (Au) as the sharp SPR curve. Numerical results are appeared that the variation of SPRF and SPR angle for improper sensing of formalin is quite negligible that confirms the absence of formalin whereas for proper sensing is considerably countable that confirms the presence of formalin. It is also shown that the sensitivity of conventional SPR sensor is 70.74% and the graphene–MoS2-based sensor is enhanced to 77% with respect conventional SPR sensor. The sensitivity is further enhanced to 79 % by including TiO2–SiO2 composite layer with respect to conventional SPR sensor. At the end of this letter, a comparative study of the sensitivity of the proposed work with the existing works is discussed. Copyright © VBRI Press.