Abstract: The International Telecommunications Union recommended the 3GPP standard use the 3GPP interleaver， it has excellent performance in Turbo codes. This paper base on the introduction of the 3GPP interleaver， then the distance spectrum of Turbo codes was analyzed， and an inproved 3GPP interleaver applied under low signal-to-noise ratio condition was presented. The simulation shows， on the condition of design steps of the basic interleaver does not change， the improve method simplify its structure， and the short frames through fill to a longer interleaver length， so the transmission BER of the shortframe at low SNR conditions was improved.