<p>Carbon-adsorbed bilayer silicene nanoribbons exhibit unique reconfigurable electronic structures due to interfacial charge transfer and orbital hybridization effects, holding significant potential for semiconductor device applications. Modulating the adsorption sites and density of carbon atoms enables precise tailoring of their band engineering and quantum transport properties. In this paper, the self-consistent charge density functional tight-binding method was used to establish two zigzag bilayer silicene nanoribbon models with different widths (6-ZSiNRs, 9-ZSiNRs). The surface atomic configuration of bilayer silicene nanoribbons and the adsorption of carbon atoms on the surface of two bilayer silicene nanoribbons were simulated. Three different adsorption methods were simulated: para-adsorption, bridge-site adsorption, and vacancy adsorption. The effects of carbon atom adsorption concentration distribution and adsorption method on the geometric structure and electronic properties of bilayer silicene nanoribbons were studied. It is found that compared with the three adsorption methods, para-position adsorption can effectively improve the binding energy of bilayer silicene nanoribbons and make the structure more stable. Bilateral adsorption can more effectively regulate the band gap of nanoribbons than unilateral adsorption. Different adsorption sites and concentrations can make the nanobelts exhibit three properties: metallic, semi-metallic, and semiconductor. The adsorption position and concentration of the carbon atoms significantly affect the charge transfer of the bilayer silicene nanoribbons. In the carbon-adsorbed atomic layer, electrons are transferred from the silicon atoms near the carbon atoms to the carbon atoms, while the atomic layer of the unadsorbed carbon atoms is mainly characterized by loss of charge and electronic neutrality.</p>