Environmental investigation in un - excavated tomb chambers may provide the scientific basis for excavation process, conservation and restoration of antiques. Before Ml tomb chamber of mausoleum ZHANG An - shi in Han Dynasty was excavated, microclimate parameters and concentrations of some atmospheric pollutants inside the chambers were monitored. The results showed that the indoor relative humidity was higher and indoor temperature, concentration of oxygen and some acidic gas pollutants were lower than those in outdoor environment. To protect the antiques being excavated, appropriate measures should be deployed, including: employing sealed container, moisture retention, and evading light. The systematic monitoring procedures and dataset obtained can also be referenced in other archaeological investigations and preservation researches.