Ice thermal energy storage (ITES) is a type of cooling thermal energy storage. It can shift the daytime peak cooling load to nighttime, thereby enhancing the economic benefit of the cooling system and enabling peak load shifting in the power grid. Although ITES has been widely utilized in district cooling systems (DCSs), the economic assessment of its implementation in DCS remains inadequate due to the thermal dynamics and operation strategy. This paper first presents an ITES-equipped DCS optimal operation model integrated with the time of use electricity price and demand charge. The proposed model can provide the economically optimal operation scheme considering the ITES dynamic charging/discharging process, and the change of the chiller's coefficient of performance, which depends on the ambient temperature and partial load rates. Then the economy of the ITES in a real DCS is assessed based on the proposed operation model. A comprehensive case study is employed to evaluate its benefit in comparison with the DCS equipped with battery energy storage. The case study indicates that the DCS with ITES outperforms in the economy, whereas DCS with battery energy storage surpasses in reducing demand charge.