The present work investigates the effect of geometrical parameters of 1D nanograting on surface plasmon resonance (SPR) and plasmonic bandgap (PBG). The use of plasmonic grating device in various electronic devices is based on correct value of bandgap energy. For this purpose, various nanograting structures having regular periodic ridges in 1D has been modeled in the form of a gold film on glass substrate using finite element analysis in RFRF Module of COMSOL (Multiphysics) 5.3a licensed version. In the designed structures, firstly, the periodicity of the grating varied while keeping the slit width and film thickness constant. Furthermore, the thickness of the grating also varied while the periodicity and slit width is kept constant and transmitted mode for each structure is studied to find the suitable value of film thickness for optimizing the device. At the end, the slit width varied while keeping the periodicity and film thickness constant. Due to increase in slit width, the bandgap energy increases until slit width equals to nearly half of periodicity after this bandgap energy decreases and associated with the sinusoidal behavior of the device which support fundamental plasmonic mode. The increase in film thickness results a linear increase in bandgap energy as long as the film thickness is comparable to the skin depth of gold and plasmonic bandgap energy is high for smaller values of periodicity and decreases with increasing periodicity. Due to the ability to control the optical properties, the PBG is expected to have a major impact on technology.