The invention discloses a GH3030 high-temperature alloy as-cast metallographic etchant and a preparing method and a using method thereof. The etchant is composed of concentrated hydrochloric acid, water and copper sulfate. The ratio of the concentrated hydrochloric acid to the water to the copper sulfate is 21-23 mL:19-21 mL:3-5 g. The metallographic structure of GH3030 high-temperature alloy can be rapidly and efficiently obtained through etching by means of the GH3030 high-temperature alloy as-cast metallographic etchant, the etching effect is good, and thus the metallographic structure of the researched and developed product can be observed. After the GH3030 high-temperature alloy is etched, the metallographic structure and a grain boundary are very clear, grains are displayed completely, and therefore manufacturing enterprises can develop new products and observe the structures of the new products; the grain size of the GH3030 high-temperature alloy can be accurately measured through a metallographic microscope, production technology parameters are adjusted and optimized through measurement of the grain size, and the product quality of the developed products is mastered and promoted.