Long noncoding RNAs (lncRNAs) are involved in vital life processes of gene expression, epigenetic regulation and X-chromosome inactivation. lncRNAs are also closely associated with tumor initiation and progression. Moreover, lncRNAs may enter human circulation system in the form of microvesicle or exosome, or in combination with RNA binding protein. Interestingly, the circulating lncRNAs are widely existed in body fluids, such as blood and urine. We review the origin of circulating lncRNAs, and the detection methods as potential biomarkers. We focus on the early diagnosis value of circulating lncRNAs as tumor biomarkers in lung, breast, gastric, liver, colorectal and prostate cancers. Compared with the traditional biomarkers, the circulating lncRNAs show the unique advantages and clinical values as novel biomarkers.