Three-dimensional numerical models of solar enhanced indirect air-cooling tower are established, and the effect of apex angle of radiators on thermo-flow performance of the tower and the varying mechanisms caused by environmental crosswind are evaluated. The distributions of air inflow and temperature fields inside and outside the tower, as well as the airflow rate and heat transfer in different cooling sectors are analyzed. The performance comparison is carried out between scenarios with and without solar radiation. The results show that, under crosswind, the flow characteristics and heat transfer properties of the tower improve with the increasing apex angle of the radiators, and the enhancement effect of solar radiation on tower performance also increases. Crosswinds enhance the performance of the radiators in the windward sector while weakening the performance of the radiators in the crosswind sector and leeward sector. Additionally, solar radiation improves the performance of the radiators in each sector, but if secondary heat transfer rate occurs in the sector, solar radiation may instead weaken the heat transfer rate performance of the radiators in that sector. When the apex angle of the radiators increases from 60° to 120°, solar radiation enhances the increase rate of the average air inflow rate of the tower at various wind speeds increase from 0.66% to 3.18%. Concurrently, the increase rate of the average heat transfer rate increase from virtually unchanged to 3.12%. The enhancement effect of solar radiation on the tower increases with apex angle of the radiators. Therefore, the tower with radiators apex angle of 120° has the optimum thermo-flow performance.