Using the method developed by Gurvitz [1996 Phys.Rev.B 53 15932],we obtained the Bloch-type rate equations describing the entire system of a periodically driving qubit monitored by a quantum point contact detector.The results demonstrate that the isolated qubit can be kept in its initial state with a large driving frequency due to more difficult electron tunneling in qubit,and this initial state can always be measured at a small measurement-induced decoherence rate during a short time. Using the method developed by Gurvitz [1996 Phys. Rev. B 53 15932], we obtained the Bloch-type rate equations describing the entire system of a driving qubit monitored by a quantum point contact detector. The results demonstrate that the isolated qubit can be kept in a large driving frequency due to more difficult electron tunneling in qubit, and this initial state can always be measured at a small measurement-induced decoherence rate during a short time.