Abstract: In LEO broadband internet systems, the satellite gNB is the core equipment to achieve seamless global coverage and ubiquitous access. The 5G NR physical layer adopts OFDM waveform, and the high-dynamic LEO environment introduces time and frequency domain deformations to OFDM signals, which cause wrong decoding for the satellite gNB. These deformations are more severe for OFDM signals with a 400 MHz bandwidth, which prevents the NTN system from supporting high-speed data services. To solve this problem, this paper first analyzes the OFDM deformations in the LEO environment, and then proposes a hardware-in-the-loop simulation platform that verifies the analysis results. The verification shows that when the equivalent sampling frequency offset caused by the LEO environment is greater than ±70 ppm, the traditional terrestrial base station receiving algorithm does not work. Finally, a resampling method is proposed to compensate for the ±70 ppm deformation. Data analysis show that with the proposed method, the sampling frequency offset reduces from ±70 ppm to ±16 ppm, and the EVM performance is improved from 21.5% to 3.2% for 16 QAM~400 MHz OFDM signal, such that satellite can decode the signal correctly.