The integrated energy system (IES) in industrial parks can achieve multi-energy complementary and coordinated optimization among various energy sources, which is of great significance for energy conservation, efficiency enhancement and carbon emission reduction. In this paper, the planning model and solution approach is proposed, considering tiered carbon trading and optimal construction timing for an industrial park''s IES containing multiple energy types, including electricity, gas and heat. Firstly, the cost calculation model for a tiered carbon trading is developed, and the ''dual-carbon'' constraints of carbon peaking and carbon neutrality are incorporated to restrict the carbon emissions of the park. Then, the optimization objective is to minimize the net present value of the total life-cycle cost, including the investment costs, operation and maintenance costs, carbon trading costs, and residual value costs. Finally, the model is solved using a mixed-integer programming algorithm to determine the investment year and capacity configuration of each component in the park’s IES. To demonstrate the effectiveness of the planning model in reducing carbon emissions and decreasing system costs, a variety of typical scenarios are established for joint comparison. Additionally, the impacts of carbon trading benchmark prices and the investment frequencies on the planning results are explored.