NOVELTY - Synthesizing biodiesel in a microorganism, comprises: cloning an Acinetobacter adipocere synthase gene, an Escherichia coli acyl-coenzyme A synthetase gene, a pyruvate decarboxylase gene and an alcohol dehydrogenase gene, respectively into a pET28b expression vector, and inserting the four genes at the downstream of a T7 promoter; obtaining a plasmid pXT9, a plasmid pXT10 and a plasmid pXT11; introducing the pXT11 into Escherichia coli; and subjecting obtained Escherichia coli strain XT31 to isopropyl beta -D-1-thiogalactopyranoside and arabinose induction.    USE - The method is useful for synthesizing biodiesel in a microorganism.    ADVANTAGE - The method: ensures microbial conversion of sugar into biodiesel and produces biodiesel through lignocellulose, and thus it provides raw material in preparation of biodiesel; does not require methanol esterification step, and thus it reduces production cost; and avoids formation of a glycerol byproduct.    DETAILED DESCRIPTION - Synthesizing biodiesel in a microorganism, comprises: (a) cloning an Acinetobacter adipocere synthase gene atfA, an Escherichia coli acyl-coenzyme A synthetase gene fadD, a pyruvate decarboxylase gene pdc and an alcohol dehydrogenase gene adhB, respectively into a pET28b expression vector, where the two ends of the gene comprises nuclear distribution gene E homolog 1 (NdeI) and Sphaerotilus natans (SpeI) enzyme restriction sites, respectively, and inserting the four genes at the downstream of a T7 promoter for T7 promoter-driven expression; (b) obtaining a plasmid pXT9 after inserting the fadD gene into an atfA gene segment containing the SpeI site, obtaining a plasmid pXT10 after inserting the adhB gene into a pdc gene segment containing the SpeI site, and obtaining a plasmid pXT11 co-expressed by the four genes, where SpeI and XbaI are isocaudomers, after inserting a pdc and an adhB gene segment into an atfA and a fadD gene segment containing the SpeI site; (c) introducing the pXT11 into a strain of Escherichia coli containing plasmids pMSD8 and pMSD15 to obtain an Escherichia coli strain XT31; and (d) synthesizing biodiesel by subjecting Escherichia coli strain XT31 to isopropyl beta -D-1-thiogalactopyranoside and arabinose induction.