Telomeres are the special structures at the ends of linear chromosomes in eukaryotic cells. Telomere length maintenance is very important for living organisms and its maintenance mechanism is a complex. Telomerase can maintain telomere length by using its own RNA template (TERC) and catalytic protein subunits (TERT) through special reverse transcriptase properties. This paper reviewed the effect of TERRA (telomeric repeat-containing RNA) on telomeric length maintenance and mechanism. First, the associations of telomere length maintenance with cell survival and aging were introduced. Second, the structure and transcription control of TERRA, TERRA-mediated RNA:DNA hybrids and formation of R-loop, the TERRA binding proteins and their functions were described. Further, the molecular mechanisms and roles of TERRA-depended telomere maintenance in life processes were discussed.