Abstract: Establishing a unified method for oxygen carrier screening is a critical step toward advancing chemical looping combustion (CLC) from laboratory research to large-scale application and accelerating the standardization of the industry. Natural ore-based oxygen carriers are currently characterized by diverse sources, considerable varia-tions in performance, and a lack of standardized evaluation criteria. In this study, more than ten ilmenite samples from different origins were systematically tested based on operational data and engineering experience obtained from a 5 MWth CLC pilot plant. By comparing their reaction performance, cyclic stability, and mechanical strength, a testing and screening procedure was developed that considers both reactivity and me-chanical strength. Unlike approaches that evaluate oxygen carriers solely on the basis of reactivity or a single laboratory indicator, the proposed method provides a more comprehensive assessment of their suitability for industrial-scale operation. Using a maximum-score benchmarking method, pilot-validated Norwegian ilmenite with an oxygen transport capacity of 3.48% and a post-reaction compressive strength of 57.71 MPa as the benchmark, ilmenites from Vietnam, Chengde, Quelimane, Buchanan, and Kalimantan Island were selected for long-term cyclic testing. The results showed that all samples became fully activated after 70 consecutive cycles at an H2 concentration of 10%. The oxygen transport capacities of the Vietnamese, Chengde, Quelimane, Bu-chanan, and Kalimantan ilmenites were 1.51%, 1.77%, 2.27%, 2.14%, and 2.06%, respectively, while their post-reaction mechanical strengths were 3.94, 3.55, 1.21, 3.24, and 3.69 N, respectively. Considering the attrition behavior of oxygen carriers during actual operation, Vietnamese ilmenite was selected for application in a 5 MWth CLC pilot demonstration plant to further verify its practical performance. The results showed that the CO2 concentration at the fuel reactor outlet was approximately 83-86%, while the oxygen replenishment rate was ap-proximately 12-15%. The carbon capture efficiency remained stable at around 90-92%, indicating that the oxy-gen carrier exhibited favorable reaction characteristics and operational stability. Overall, the test performance was satisfactory, confirming the feasibility of the proposed screening procedure. These findings provide im-portant data and engineering guidance for establishing unified testing standards, screening criteria, and perfor-mance evaluation systems for oxygen carriers in the CLC industry