In this paper, orthogonal frequency division mul-tiplexing with index modulation (OFDM-IM) aided generalized polarization modulation is proposed for low-earth-orbit (LEO) satellite security communications, which strengthens legitimate link security by exploiting the frozen bit activation pattern in the polar code. Specifically, the frozen bit activation pattern is determined by the transmission channel undergoing a four-stage transformation, which decomposes the channel into a series of bit-polarized channels through subblock-(index-symbol)-modulation-bit partitioning. Next, the frozen bit generation method is conceived to exploit chaotic mapping by using the channel state information as the initial value. Finally, simulation results verify that the proposed system significantly enhances transmission security while maintaining competitive bit error rate (BER) and peak-to-average power ratio (PAPR) performance. Index Terms—Orthogonal frequency division multiplexing with index modulation (OFDM-IM), generalized polarization modulation , security, peak-to-average power ratio (PAPR), LEO satellite communications.