Photothermal interference (PTI) is a new optical method for gas detection. Due to its high sensitivity,high accuracy,and "zero background" advantages,it is expected to be promoted and applied in the field of dissolved gas analysis (DGA). However,the influence of the temperature and pressure of dissolved gases in oil on the photothermal phase is not yet clear. To improve the applicability of PTI technology in the DGA,an intensity-modulated-PTI-based acetylene sensing scheme using a Herriott cell is proposed. Experimental measurements are conducted on mixed gases containing acetylene and other characteristic gases to simulate fault conditions in transformer oil,and the influence of temperature and pressure on the detection results during the measurement process is focused. It is found that the photothermal phase increases with decreasing temperature or increasing pressure. Therefore,the accuracy and stability of acetylene detection depend on the reasonable setting of temperature and pressure during the detection process. The system demonstrates a strong linear relationship with acetylene concentration,with a detection sensitivity of 0.151 mV/(μL·L^-1) and a detection lower limit of 5.3 μL/L. The proposed solution provides insights and lays the foundation for the future development of a new type of DGA based on PTI technology.