In this work, low frequency noise (LFN) in Schottky junction trigate silicon nanowire (SiNW) field-effect transistors (FETs) (SJGFETs) fabricated on bonded silicon on insulator (SOI) substrate is systematically analyzed. The LFN exhibited a typical 1/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}$ </tex-math></inline-formula> spectrum and can be well described by the carrier number fluctuation (CNF) with correlated mobility fluctuation (CMF) model. It was found that CNF is the dominant component of the LFN, while CMF associated with the Coulomb scattering near the buried oxide (BOX)/SiNW channel interface plays an insignificant role. Applying a substrate bias can further modulate the LFN of the SJGFETs, and the effect is ascribed to the nonuniform energy distribution of the BOX/SiNW channel interface traps. Confining current path in the channel bulk away from the interface brought limited gain in terms of LFN performance. Finally, our experimental results suggested a possible transition of CMF mechanism from Coulomb scattering to surface roughness scattering when the current path is pushed away from the BOX/SiNW channel interface to the channel bulk.