The invention belongs to the technology field of the reactive dye, in particular to the synthetic method of the sulfonation para-ester. The synthetic method of the sulfonation para-ester comprises sulfonation, hydrolysis, dilution, purification, neutralizing salting-out and filtration and over dry. The difference with the prior art is that the control temperature is always not more than 5 DEG C. in the unit operations of dilution, filtration and neutralizing salting-out; the diatomite with volume of 0.6 to 0.7 per cent of the total volume of the reaction solution is added after dilution, and perform filter processing after stirring evenly; the filter cake is adjusted to pulping by water and the pH value is adjusted equal to 6.0 to 6.5 by 20 per cent to 30 per cent sodium bicarbonate solution; the potassium chloride is added based on 7 per cent to 8 per cent of the total volume of the reaction solution to do salting-out; the filter cake is kept after filtration and is dried under the temperature of 80 DEG C. to 85 DEG C.. The adoption of the synthetic method of the sulfonation para-ester of the invention basically avoids the hydrolysis of the ester, filters the impurities such as the byproduct, improves the product quality and realizes the dryness of the product.