The invention discloses an amide compound application, an extraction composition with an amide compound and an extraction system. The extraction composition comprises N,N-diethylpropionamide and a thinner and does not include neutral phosphorus oxide as shown in the formula A. The amide compound or the extraction composition with the amide compound can extract and reextract lithium from Li-containing brine, and the Li extraction rate of the Li-containing brine is 83.65% or above. The Li-Mg partition coefficient reaches high to 297 or above. When HCl is used for conducting Li reextraction, thereextraction rate is 84.18% or above, corrosion to equipment is small, and the amide compound application, the extraction composition with the amide compound and the extraction system are suitable formeeting the industrialized operation requirements (please see the specification for the formula).