In order to understand the status of preservation of current historical relics, a complete system of wireless sensors was built in the Tianjin Museum to monitor the microenvironment inside showcases in January, 2015. Monitoring parameters included the temperature and relative humidity of the air, the light intensity, the ultraviolet radiation and the concentrations of air pollutants inside the showcases. Based on the insitu test results, some critical issues relevant to monitoring and control of the preservation environment of historical relics were evaluated and analyzed. Results showed that the individual showcases had a relatively high humidity ranging from 60.4% to 63.3%, which is not good for preservation of historical relics. It was suggested that hygroscopic materials should be used to control the humidity in the showcases. The illuminance was 1.84lx when the museum closed; when the museum opened, the illuminance and ultraviolet radiation intensity ranged from 43.96 to 52.22lx and from 0.02 to 0.06μW/cm², respectively, which meet the requirements of the Code for Lighting Design of Museums (GB/T 23863—2009).The carbon dioxide concentration in the exhibition hall was affected by the number of persons present, reaching a maximum at 12∶00~14∶00 and then decreasing. The cumulative phenomenon of volatile organic compounds concentration was found in the showcases. The results can provide reference for improving the protection level of cultural relic.