The invention relates to the technical field of heat exchangers, in particular to a high-efficient all aluminum alloy heat exchanger which comprises a housing, and a main fluid inlet pipe, a main fluid outlet pipe, a heat exchanging medium inlet pipe and a heat exchanging medium outlet pipe, which are connected externally with the housing. At least one all aluminum alloy heat exchanging sheet which is formed by the extrusion process is arranged in the housing; each heat exchanging sheet is provided with a heat exchanging fin and a nick; the middle of each heat exchanging sheet is provided with a seamless millipore passage in the length direction; the seamless millipore passage and the main fluid inlet pipe are communicated with the main fluid outlet pipe so as to form a main fluid passage; and clearances between the nicks of the heat exchanging sheets and the heat exchanging fins, clearances between adjacent heat exchanging sheets, the heat exchanging medium inlet pipe and the heat exchanging medium outlet pipe together form a heat exchanging medium passage. The invention has the advantages of good heat transfer performance, high voltage resistance, low temperature resistance, low cost and stable operation, can be used in oil refining engineering, chemical engineering, low temperature engineering, liquefaction of natural gas, liquid vaporization, gas separation and other industrial fields, and can be used for super-low temperature gas liquefaction or liquid vaporization.