Abstract: UBS memorizing in-situ CBM detector is used to detect the concentration, pressure and temperature of in-situ CBM. The detector, with a ATmega8 chip as the core of the detection circuit, is powered by batteries and started by Hall alnico. After the rubber is set, detected in-situ gas pressure, temperature and detection time are saved in UBS. Gas is collected in special canisters for analysis of gas composition and concentration in lab. The experiments showed that the detector operated stably and could meet the engineering requirements.