In wireless communication systems, frame synchronization is one of the key technologies for achieving reliable communication. However, an excessively low signal-to-noise ratio (SNR) and severe Doppler frequency offset can significantly impact the success rate of system synchronization. Compared to continuous communication, discontinuous communication requires real-time and reliable synchronization within an extremely short period, which imposes higher requirements on frame synchronization design. To address these issues, a frame structure based on a dual-spread spectrum preamble is designed. The adopted two-pass spreading and differential encoding techniques enable preamble acquisition at low SNR. A proposed frequency offset estimation and compensation algorithm, combining coarse and fine methods in the time-frequency domain, can eliminate the impact of large Doppler shifts on frame synchronization. Furthermore, an adaptive threshold strategy is utilized to further ensure the reliability of synchronization. Simulation results show that under the conditions of a -5dB SNR, a 12kHz Doppler shift, and a short communication duration of 0.5s, the frame synchronization success rate reaches 99.3%, meeting the requirements of the communication system.