A novel dual-channel photovoltaic/thermal (PV/T) system featured by a nanofluid-based spectrum splitting top channel and an S-shaped bottom channel (Model A) was proposed. The temperature uniformity of PV panel and performance of Model A under different structural and operational parameters were discussed through 3-D numerical simulation. To quantitatively reflect the temperature uniformity of PV panel, two evaluation criteria were presented. The performance of Model A was compared with that of PV/T system with two rectangular channels above/below PV panel (Model B) and PV/T system only with an S-shaped channel below PV panel (Model C). The results illustrate that mass flow rate has the greatest influence on temperature uniformity, whilst the influence of inlet temperature and wind velocity is much lesser. The optimal values of the optical nanofluid thickness and mass flow rate are 10 mm and 0.008 kg/s, at which the total energy efficiency and overall exergy efficiency reaching maximum of 86.97% and 13.80% respectively. The temperature uniformity of PV panel in Model A is better than Model B and Model C, besides, the total energy efficiency of Model A is 0.2% and 3.17% higher than those of Model B and Model C in a certain condition. (c) 2020 Elsevier Ltd. All rights reserved.