The utility model discloses a quality of water total mercury detection device, the shell comprises an upper shell and a lower shell, the epitheca passes through buckle joint in inferior valve top, inferior valve internally mounted has double glazing water storage tank, catalysis pipe, absorption tube, vacuum pump and waste gas to collect processing apparatus, double glazing water storage tank upper end communicates in catalysis pipe one end through the connecting pipe, catalysis pipe one end communicates in the absorption tube, absorption tube one end is passed through the connecting pipe andis communicate in the vacuum pump input. Inside gas after the response measurement got into and collects the first process chamber among the processing apparatus to waste gas, the sulphide solution inside with first process chamber mixed reaction, got rid of remaining mercury in the gas, the gaseous second process chamber that gets into after the processing, and remaining sulphide in the gas is got rid of in the alkaline solution reaction inside with the second process chamber, finally collects to the gasbag, collects to the gas of gasbag and to carry out further detection, records the purification degree of gas, can carry out gaseous emission after qualifiedly.