The invention belongs to the spectrum detection field and particularly relates to an internal combustion engine cylinder internal pressure and temperature test method based on a tunable semiconductor laser device spectrum absorption method and a device. The method comprises steps that for a gas component in a cylinder, a tunable semiconductor laser device including a gas component absorption peak is selected, laser emitted by the laser device penetrates through the internal combustion engine cylinder, absorption lines of the internal combustion engine cylinder after gas absorption is detected through utilizing a photoelectric detector, internal pressure and a temperature value of the internal combustion engine cylinder are measured according to linewidth values of the acquired absorption lines, so the internal pressure and the temperature are measured online in real time. The method is advantaged in that problems of complex work process and bad work environment factors on measurement errors can be excellently solved, the internal pressure value and the temperature value of the internal combustion engine cylinder can be effectively and accurately measured, and the method is suitable for detecting the information of pressure and temperature of the internal combustion engine cylinder in real time.