Here we report GT (Guanin/Thymine) standard (GTS) for plasmid construction under which DNA sequences are defined as two types of standard, reusable parts (fragment and barcode). We develop a technology that can efficiently add any two barcodes to two ends of any fragment without leaving scars in most cases. We can assemble up to seven such barcoded fragments into one plasmid by using one of the existing DNA assembly methods, including CLIVA, Gibson assembly, In-fusion cloning, and restriction enzyme-based methods. Plasmids constructed under GTS can be easily edited, and/or be further assembled into more complex plasmids by using standard DNA oligonucleotides (oligos). Based on 436 plasmids we constructed under GTS, the averaged accuracy of the workflow was 85.9%. GTS can also construct a library of plasmids from a set of fragments and barcodes combinatorically, which has been demonstrated to be useful for optimizing metabolic pathways.