Abstract: A sample adding system for automatically adding a sputum digestion liquid includes a weighing device provided with a weight sensor and a sample adding device. A liquid inlet of a sample adding tube goes deep into the sputum digestion liquid reagent bottle, and a liquid outlet of the sample adding tube extends to a position above the weighing device. A sample adding needle is connected to the liquid outlet of the sample adding tube. The sample adding tube is equipped with a quantitative sample adding pump. A signal output end of the weight sensor is electrically connected to a signal input end of a single-chip microcomputer, and a control output end of the single-chip microcomputer is electrically connected to a control input end of the quantitative sample adding pump.