The 3-qubit error-correction quantum circuit is realized and optimized in the non-measuring condition. The modular thought is presented to design and optimize the quantum error-correction circuit. With the quantum bits increasing, the error-correction circuit of 3-qubits can be used in the error-correction circuit of 5-qubits as a module. The error-correction circuit of 5-qubits can be used in the error-correction circuit of 7-qubits. By parity of reasoning, the error-correction circuit of a few quantum bits can be used in the error-correction circuit of multiple quantum bits. The quantum error-correction circuit can be simplified and the redundant qubits can be reduced using the method. It can also make the quantum cost lower.