A process for the preparation of gadolinium complex of -4-(4-Ethoxybenzyl)-3,6,9-tris(carboxylatomethyl)-3,6,9-triazaundecanedioic acid disodium (Gadoxetate disodium) of formula 1 comprising the steps of: i) protecting amino group of L-tyrosine of formula 12 with di-tert-butyl dicarbonate (BoczO) in presence of base to get boc-protected L-tyrosine of formula 13; ii) alkylating Boc-protected L-tyrosine of formula 13 with diethyl sulfate in a suitable solvent to obtain formula 14; iii) converting formula 14 in to anhydride or ester in situ by reacting with suitable reagent followed by reduction with reducing agent to obtain -tert-butyl (1-(4-ethoxyphenyl)-3-hydroxypropan -2-yl) carbamate of formula 15; iv) protecting hydroxyl group in -tert-butyl (1-(4-ethoxyphenyl)-3-hydroxypropan -2-yl) carbamate with methanesulfonyl chloride in presence of base to obtain -2-((tert-butoxycarbonyl)amino)-3-(4-ethoxyphenyl) propyl methanesulfonate of formula 16; v) condensing -2-((tert-butoxy carbonyl) amino)-3-(4-ethoxyphenyl) propylmethane sulfonate of formula 16 with ethylenediamine in a suitable solvent to obtain -tert-butyl (1-((2-aminoethyl) amino)-3-(4-ethoxyphenyl)propan-2-yl)carbamate of formula 17; vi) deprotecting amino protecting from -tert-butyl (1-((2-aminoethyl) amino)-3-(4-ethoxyphenyl) propan-2-yl)carbamate using suitable acid to obtain -N1-(2-aminoethyl)-3-(4-ethoxyphenyl)propane-1,2-diamine acid salt of formula 18, which is further converted in to free base of formula 18a in situ optionally, by reaction with a suitable base; vii) alkylating -N1-(2-aminoethyl)-3-(4-ethoxyphenyl) propane-1,2-diamine acid salt or free base with tertiary butyl bromoacetate in presence of potassium carbonate to provide - tert- butyl 2,2'-(2- ((2-(bis(2 -tert-butoxy- 2-oxoethyl) amino)-3-(4-ethoxyphenyl)propyl) (2-tert-butoxy-2-oxoethyl)amino) ethyl azanediyl) diacetate of formula 3; viii) deprotecting tertiary butyl group of -tert- butyl 2,2'-(2-((2-(bis(2-tert-butoxy- 2-oxoethyl) amino)-3-(4-ethoxyphenyl)propyl) (2-tert-butoxy-2-oxoethyl)amino) ethyl azanediyl) diacetate of formula 3 with aqueous sodium hydroxide to obtain -2,2'-((2-((2-(bis(carboxymethyl)amino)-3-(4-ethoxyphenyl)propyl) (carboxymethyl) amino)ethyl)azanediyl)diacetic acid of formula 4; ix) converting -2,2'-((2-((2-(bis(carboxymethyl)amino)-3-(4-ethoxyphenyl) propyl) (carboxymethyl) amino)ethyl)azanediyl)diacetic acid of formula 4 to Gadolinium salt by treating with Gadolinium oxide in presence of sodium hydroxide. i) protecting amino group of L-tyrosine of formula 12 with di-tert-butyl dicarbonate (BoczO) in presence of base to get boc-protected L-tyrosine of formula 13; ii) alkylating Boc-protected L-tyrosine of formula 13 with diethyl sulfate in a suitable solvent to obtain formula 14; iii) converting formula 14 in to anhydride or ester in situ by reacting with suitable reagent followed by reduction with reducing agent to obtain -tert-butyl (1-(4-ethoxyphenyl)-3-hydroxypropan -2-yl) carbamate of formula 15; iv) protecting hydroxyl group in -tert-butyl (1-(4-ethoxyphenyl)-3-hydroxypropan -2-yl) carbamate with methanesulfonyl chloride in presence of base to obtain -2-((tert-butoxycarbonyl)amino)-3-(4-ethoxyphenyl) propyl methanesulfonate of formula 16; v) condensing -2-((tert-butoxy carbonyl) amino)-3-(4-ethoxyphenyl) propylmethane sulfonate of formula 16 with ethylenediamine in a suitable solvent to obtain -tert-butyl (1-((2-aminoethyl) amino)-3-(4-ethoxyphenyl)propan-2-yl)carbamate of formula 17; vi) deprotecting amino protecting from -tert-butyl (1-((2-aminoethyl) amino)-3-(4-ethoxyphenyl) propan-2-yl)carbamate using suitable acid to obtain -N1-(2-aminoethyl)-3-(4-ethoxyphenyl)propane-1,2-diamine acid salt of formula 18, which is further converted in to free base of formula 18a in situ optionally, by reaction with a suitable base; vii) alkylating -N1-(2-aminoethyl)-3-(4-ethoxyphenyl) propane-1,2-diamine acid salt or free base with tertiary butyl bromoacetate in presence of potassium carbonate to provide - tert- butyl 2,2'-(2- ((2-(bis(2 -tert-butoxy- 2-oxoethyl) amino)-3-(4-ethoxyphenyl)propyl) (2-tert-butoxy-2-oxoethyl)amino) ethyl azanediyl) diacetate of formula 3; viii) deprotecting tertiary butyl group of -tert- butyl 2,2'-(2-((2-(bis(2-tert-butoxy- 2-oxoethyl) amino)-3-(4-ethoxyphenyl)propyl) (2-tert-butoxy-2-oxoethyl)amino) ethyl azanediyl) diacetate of formula 3 with aqueous sodium hydroxide to obtain -2,2'-((2-((2-(bis(carboxymethyl)amino)-3-(4-ethoxyphenyl)propyl) (carboxymethyl) amino)ethyl)azanediyl)diacetic acid of formula 4; ix) converting -2,2'-((2-((2-(bis(carboxymethyl)amino)-3-(4-ethoxyphenyl) propyl) (carboxymethyl) amino)ethyl)azanediyl)diacetic acid of formula 4 to Gadolinium salt by treating with Gadolinium oxide in presence of sodium hydroxide.