The invention relates to tert-octyl salicylaldoxime and a synthetic method thereof. The synthetic process conditions are as follows: the molar ratio of magnesium: p-tert-octyl phenol is 0.55:1, the salt forming reaction time is 110 minutes and the salt forming reaction temperature is 63 DEG C; the molar ratio of paraformaldehyde: p-tert-octyl phenol is 2.4:1, the acylation temperature is controlled to be 107 DEG C by oil bath, and the time is 150 minutes; the molar ratio of hydroxylamine hydrochloride: p-tert-octyl phenol is 1.5:1, the oximation reaction temperature is between 45 DEG C and 50 DEG C, the boil bath temperature is 47 DEG C, and the time is 210 minutes; adding methylbenzene for two times while methanol-methylbenzene azeotrope is distilled in the salt forming reaction, and adding the methylbenzene for three times in the acylation reaction, wherein 5 ml of the methylbenzene is added every time, and the time interval is 2 minutes; to obtain a tert-octyl salicylaldoxime coarse product, acidifying, distilling in the reduced pressure and washing by petroleum ether, to obtain the tert-octyl salicylaldoxime. Compared with other common copper extraction agents, the tert-octyl salicylaldoxime has the advantages of low synthesis cost and extensive raw material source.