Ionospheric anomalies can seriously threaten important flight phases such as approach and landing, so accurate real-time monitoring is necessary. In this paper, an ionospheric anomaly gradient detection platform is designed for satellite navigation receiver. Based on GNSS observation data, the spatial gradient of ionospheric vertical total electron content is calculated, and anomaly ionospheric gradient is detected using generalized likelihood ratio test method. To verify the correctness of detection results, rate of TEC change index is also calculated for comparison. Simulation results show that the platform can detect ionospheric anomaly gradient state fast and accurately, and the proposed approach can used by GNSS receivers to detect ionospheric anomaly.