Liquid biopsy is an emerging and promising detection tool for cancer, with the benefit of being non-invasive and convenient. It analyzes tumor-derived information in the blood or other body fluids including circulating tumour cells (CTCs), circulating tumour DNA (ctDNA) and exosomes. Nowadays, with the expansion of liquid biopsy research contents and the development of capture and detection technologies, liquid biopsy is increasingly utilized in clinical applications, promoting the development of tumor precision medicine. Here, we mainly focus on reviewing the objects and technologies about liquid biopsy, as well as its applications, development and challenges in clinical practices.