In order to reduce the impact of X-ray flares on the satellite-terrestrial quantum communication link, this paper proposes a quantum satellite switching strategy based on the optimal invisible transmission fidelity. Based on the variation relationship between amplitude-damped noise fidelity, phase-damped noise fidelity, bit-flip noise fidelity, and depolarising noise fidelity and the X-ray radiation flux, the article selects an appropriate fusion factor to fuse the four fidelities into one variable called the actual channel fidelity. The actual channel fidelity corresponding to 60 dB link attenuation is taken as the minimum threshold for quantum satellite switching, and during the satellite switching process, one quantum satellite is always available to provide services for ground users, and the one with the largest actual fidelity is selected among the candidate quantum satellites as the replacement satellite for another quantum satellite. It is shown that the algorithm can improve the quantum satellite switching success rate and reduce the dropout rate to a certain extent, and improve the effectiveness of the star-ground quantum communication link under the interference of X-ray flares, compared with that of not taking into account the actual channel fidelity as a quantum satellite switching condition.