In order to investigate the influence of environmental temperature and humidity on operation period of low density ablator, the low density prefabrication has been perfused, cured and manufactured after placing in different times under the indoor situation, and further discussed the influences of viscosity on micro and macro appearances of ablator and process technologies.The results show that the viscosity is increasing with the temperature and humidity, and there is an inflexion point in this process. The humidity and temperature have more impact on viscosity after the inflexion point.The higher temperature and humidity are, the higher rising rate will be.The densities and macro appearance around inflexion point has no clear distinction. The fillers are uniform distributed and fully infiltrated by the resin before the inflexion point.Conversely, the fillers are uneven distributed and partly infiltrated, and the resin remains in micro-pores after the inflexion point. Therefore, the prefabrication must be perfused into honeycomb before the viscosity of resin reached its inflexion. The higher temperature and humidity are, the shorter operation period is.And the reverse is also true.