This letter investigates the secrecy performance of a satellite wiretap channel with multi-user opportunistic scheduling. By considering some practical effects, such as satellite multi-beam pattern and path loss, and assuming that the satellite channel undergoes Shadowed-Rician fading with the channel parameters being integer, we derive closed-form expressions of the probability of non-zero secrecy capacity, the secrecy outage probability and the average secrecy capacity for the satellite wiretap channels. Numerical results confirm the correctness and effectiveness of the secrecy performance analysis.