The ionospheric scatter channel exhibits wide signal-to-noise ratio variations and severe frequency-selective fading, resulting in reduced transmission efficiency (TE). We propose a symbol shortening transmission algorithm (SSTA) for single carrier interleaved frequency division multiple access (SC-IFDMA) systems by removing the cyclic prefix (CP) and shortening the partial periodic data symbols. Owing to the superposition of multi-users with different phase rotation (PR), the received data loses the periodic feature. A novel symbol restoration algorithm is proposed by using received clean data symbols (CS) with cyclic-shift property (CSP) to restore shortening data symbols (SS) and received dirty data symbols (DS) without CSP that are affected by the multipath channel. The simulation results show that SSTA can be improved by approximately 1.2 dB compared to the conventional algorithm at a bit error rate (BER) of $10^{-3}$ . Meanwhile, SSTA can substantially improve the TE of the SC-IFDMA system by a factor of two and more while minimally affecting BER.