Under different initial states, the time evolution of quantum state fidelity of C atom and H atom was discussed based on magnetic resonance force microscopy (MRFM) system. The results show that the time evolution curve of fidelity is different under the different conditions of initial states. Both deviation of the magnetic field due to the cantilever offset and interaction of spins and RF magnetic field make the period of fidelity decrease greatly. Consequently the quantum information can return its initial state in a short time interval. At the same time the RF magnetic field can make the quantum information approach ideal states in the transmission process that provides particular guidance for detecting atomic states in the sample and improving the accuracy of information in transmission process.