4',4 ''(5 '')-Di-tert-butyldibenzo-18-crown-6 (DTBB18C6) was synthesized by improving the electrophilic aromatic substitution of dibenzo-18-crown-6 (DB18C6) using tert-butyl alcohol (TBA) as alkylation reagent, H3PO4 (85 wt%) as catalyst and CH2Cl2 as solvent. Experimental results show that the optimized reaction conditions were 0.03 mol L-1 for TBA concentration, 2.5 for TBA/DB18C6 molar ratio, 0.006 mol L-1 for H3PO4 concentration, 50 degrees C reaction temperature, and 6 h reaction time. Under the optimum reaction conditions, DTBB18C6 yield can reach 43.65%.