During the development of tight sandstone gas reservoirs, wellbore chemicals are injected into the wellbore and enter the reservoir. Wellbore chemicals undergo different temperature and pressure conditions as they enter the reservoir, so it is necessary to clarify the changes in the properties of on-site chemicals under different temperature and pressure conditions. This study investigated the pH, surface tension, and viscosity changes of different wellbore chemicals including surfactants, corrosion inhibitors, anti-blocking agents, and modifiers at different temperatures and pressures. The study found that the properties of the injected chemicals, except for modifiers, changed with increasing temperature, characterized by decreasing pH, increasing acidity, and decreasing surface tension and viscosity. The properties of modifiers remained relatively stable with temperature changes. It was also found that pressure had little influence on the properties of different chemicals. The research results clarify the changes in the properties of different chemicals during injection, which is of significant reference value for on-site implementation of different chemicals considering temperature and pressure effects.