Provided in the present invention is a composition of detection agents for living cells, especially epithelial tumour cells; the composition contains 0 - 5% folic acid, 0 - 10% folic acid composite, 0.01 - 5% methylene blue, 0.1 - 10% sugar reducing agent, 2 - 6% acetic acid and 3 - 95% water. Also provided in the present invention is a preparation method for the composition of detection agents, and kits containing the composition of detection agents.