Multipass cells are largely used in absorption spectrometry technique to improve gas detection sensitivity and reduce detection limit. A novel multipass cell is presented by combining both the advantages of traditional Herriott cell and White cell. It employs White cell′s optical threemirrorstructure and Herriott cell′s beam reflection mechanism. The novel multipass cell possesses features of miniaturizable, simple and compact structure, easily adjustable optical path, and stable performance. The new cell with basal length of 20 cm and adjustable optical path from 10 to 100 m is utilized as the gas absorption cell in a tunable diode laser absorption spectrometry (TDLAS) system for high sensitive detection of CO. The detection limit of CO can be further improved down to 10^{-6 level with the help of digital signal processing technique. The experiment shows the new cell has an important role in absorption spectrometry technique and it can improve obviously gas detection sensitivity compared with traditional multipass cells.}