Based on the prototype of Manzanares solar chimney power generation system in Spain, the influence of the chimney shape, collector diameter and collector’s height from ground on the flow and heat transfer characteristics of solar chimney power plant system were numerically simulated. The results showed that: The maximum velocity is highest but the stable velocity is lowest in the central axis of diverging chimney. The central temperature in the diverging and converging chimney is higher than that in the straight chimney. The mass flow rate in the converging chimney is minimum but the total heat transfer rate is maximum in the diverging chimney. Comprehensive consideration suggests that the diverging design of chimney is beneficial to improve the flow rate and overall heat transfer rate. Increasing of collectors diameter significantly enhances the flow and heat transfer characteristics of the system, but the enhancement effect gradually weakens with the increasing of collectors diameter. The increased degree of the center velocity and center temperature decrease with the increasing outer height of collectors.