The solar air collector assisted air source heat pump is demonstrated to be an efficient clean heating technology, while the research on its working modes, and the corresponding energy, exergy, economic, environmental (4E) analysis is insufficient. In this study, a novel triangular solar air collector assisted air source heat pump (TSAHP) for building heating is proposed, and three working modes including preheating, series and parallel modes are illustrated. The energy model is established and used to determine the optimal working mode, and solved by Python environment. Four scenarios including TSAHP with three areas of triangular solar air collector (TSAC) and conventional air source heat pump (ASHP) are compared based on the optimal working mode. Thermodynamic performance of the four scenarios under different working conditions is analyzed, and result indicate that the TSAHP with 3 m2 TSAC can reduce the power consumption and exergy destruction of ASHP components by 321.9 kWh and 784.6 MJ respectively during the whole heating period. Economic evaluation shows that TSAHP has the shortest payback period with moderate TSAC area, and has economic advantages at low nominal interest rate and high electric power cost with large TSAC area. In addition, based on the whole life cycle, 1 m2 of TSAC can reduce CO2 emission by more than 4500 kg.