Nitrogen oxides have become one of the main pollutants along with the growth of the city automobiles in recent years. The effects of nitrogen oxides on cultural materials are also much noticed by conservator. This paper introduced the harmful action of nitrogen oxides including nitrogen dioxide, nitric acid in gaseous state and secondary pollutants (Ozone and PAN) produced by nitrogen oxides etc. Also the pattern the concentration change of nitrogen oxides a the laboratory surroundings in respect to sampling time, site and weather (sunny or rainy) have been studied by using NOx analyzer. The results showed that the peak concentration of nitrogen oxides is between 6:00 to 9:00 every morning and 15:00 to 17:30 every evening. The analysis of the daily concentration change of NO2 to NO showed that the first peak of NO2 appeared between 6:00 to 8:00, the first peak of NO was postponed 1 hour later and appeared between 7:00 to 9:00. The observation also showed that the NOx pollutants in sunny days is more serious than in rainy day, the concentration change is closely related to the site of sampling. In the paper the problem of where the NOx comes from and why the peak of NO appears lately has been discussed. This study will help the conservator to select the proper time to carry and treat cultural materials, and also to select proper sampling site.