Low-temperature stretching testing system and testing method

The invention belongs to a testing system and a testing method, and concretely relates to a low-temperature stretching testing system and a testing method. The testing system comprises an outer Dewar and an inner Dewar, a Dewar seal cover is arranged at the top, an external bile liquid conveying tube and an internal bile liquid conveying tube are arranged on the low-temperature stretching testing system, the external bile liquid conveying tube is communicated with the space between the outer Dewar and the inner Dewar, the internal bile liquid conveying tube is communicated with the space in the inner Dewar, an external bile liquid conveying tube control valve and a liquid conveying tube main valve are arranged on a pipeline of the external bile liquid conveying tube in order, the internal bile liquid conveying tube enables airtight communication with the liquid conveying tube main valve, an external bile liquid nitrogen exhaust pipe and an internal bile liquid nitrogen exhaust pipe are arranged on the low tem