This paper proposes a natural gas assisted solar low-concentrating photovoltaic/thermal trigeneration (NG-LCPV/T-TG) system. This novel system simultaneously provides electrical, thermal and cooling energy to the user. The design and dynamic simulation performance of the NG-LCPV/T-TG system is completed using Transient System Simulation (TRNSYS) software. The results show that the system can satisfy the requirements of the cooling and heating load. The proposed system maintains the experimental room temperature at about 25 °C under the cooling mode, at about 20 °C under the heating mode. The electrical and thermal energy produced by the low-concentrating photovoltaic/thermal (LCPV/T) system are 3819 kWh and 18,374 kWh. Meanwhile, the maximum coefficient of performance (COP) of the low temperature heat pump (LHP), high temperature heat pump (HHP) and chiller are 5, 2.2 and 0.6, respectively. This proposed system realizes the coupling of natural gas and solar energy in a building. In summary, this trigeneration system is feasible and it promotes the implementation of building integrated high-efficiency energy supply system.