CO2 capture and storage (CCS) has been identified as a critical and promising option for power generation in a carbon-constrained world. Flexible-operation mechanism of CO2 capture power plant is of great significance no matter in enhancing economic returns of plant investment or in ensuring the secure operation of power system. In this paper, the feasibility, mechanism, and options of flexible operation in capture plant are first clarified. Then, based on a benchmark capture plant with postcombustion and solvent/sorbent separation technology, a generic quantitative model is established to formulate the process of CO2 capture and the interaction between capture system and generation system. Plant performances as well as its effects on power-system operation are examined, revealing the different characteristics between CO2 capture power plant and conventional noncapture plants. On this basis, typical operation modes of CO2-capture power plant are defined and identified. In the end, a numerical case is studied to testify the effectiveness of the proposed model.