Disclosed is a diacylglycerol acyltransferase 1, a recombinant Saccharomyces cerevisiae containing the diacylglycerol acyltransferase 1, and application thereof in production of triacylglycerol. The diacylglycerol acyltransferase 1 of the invention has a function of catalyzing synthesis of triacylglycerol. After the recombinant Saccharomyces cerevisiae containing the diacylglycerol acyltransferase 1 of the invention is subjected to induction culture for 48 h, the content of total fatty acid and triacylglycerol in the recombinant Saccharomyces cerevisiae containing the diacylglycerol acyltransferase 1 can be respectively increased by 1.94 folds and 12.09 folds as compared with those of Saccharomyces cerevisiae without the recombinant diacylglycerol acyltransferase 1. The instant invention provides a method for improving the ability of microorganisms to produce polyunsaturated fatty acids (PUFAs) by means of genetic engineering.