Cotton (Gossypium hirsutum L.) is an important crop in the world and increasing its fiber quality is very cr-ucial for textile industries. Spider silk is the strongest and most elastic fiber ever known in the nature. Cotton is one of the main crops in the world and increasing its fiber quality is very important for textile industries. In this regard, a synt-hetic construct has been designed to offer spider silk quality to cotton fibers by fiber-specific expression of Major am-pullate spidroin1 (MaSp1) gene under control of core sequence of GaRD22-like1 promoter. The synthetic construct was double digested by the EcoRI and NheI and sub-cloned in pCAMBIA1304 binary vector. E.coli DH5α was transformed using new plasmid namely pCSP. Ligation and intact backbone of plasmid was conformed using MaSp1 and hygrom-ycin re-sistance genes specific primers and finally with EcoRI/NheI double digestion. Agrobacterium tumefaciens LBA4404 was transformed with pCSP to transform cotton ovules of Varamin cultivar. The expression of MaSp1 in co-tton ovules and fibers showed that this synthetic sequence had been successfully expressed under control of GaRDL1 core promoter and this construct without codon optimization could be used for cotton transformation and its fiber qual-ity manipulation.