The invention relates to an automatic stretching alignment device for synchrotron radiation in-situ test. The device is characterized by further comprising an automatic alignment control device, wherein the automatic alignment control device comprises an alignment control sliding plate capable of sliding on a bottom plate and with a sample cavity placement opening which does not contact with a sample heater during sliding in a part corresponding to the sample heater, two displacement sensors arranged on two clamping blocks of a bidirectionally and synchronously sliding clamping stretching mechanism respectively, an automatic alignment controller of which the input end and the output end are connected with the output ends of the displacement sensors and the input end of an alignment motor respectively, and an alignment transmission mechanism connected between the alignment motor and the alignment control sliding plate; the bidirectionally and synchronously sliding clamping stretching mechanism is arranged on the alignment control sliding plate; a stress sensor is arranged on one clamping block of the bidirectionally and synchronously sliding clamping stretching mechanism. A tested point of a tested sample can be ensured to be at a detection point of the test device in a synchrotron radiation in-situ test process.