Concentrating solar power (CSP) plant, which has great controllability and scheduling flexibility, is a promising renewable energy power generation technology. The reasonable scheduling of a CSP plant can effectively reduce the operating cost of the integrated energy system (IES). In this context, a day-ahead optimal coordinative operation model of the electric–thermal–gas IES considering CSP plant is proposed in this study with the objective function of minimising the operating cost of the IES. In the proposed model, the transmission delay characteristic of the thermal network is considered to reflect the large thermal inertia of the thermal network. Then, the incremental formulation for the piecewise linearisation and the second-order cone relaxation method are utilised to transform the proposed non-linear model into a mixed integer quadratically constrained programming model, which can be efficiently solved by CPLEX solver. The case study shows that the optimal operation model considering CSP plant has better performance in reducing the operating cost and promoting the wind power penetration when compared with the model considering photovoltaic. In addition, the scheduling flexibility of IES can be enhanced by the virtual thermal energy storage characteristic of the thermal network to reduce the operating cost and promote the wind power penetration of IES.