The development of a modified method to produce heat treated twisted nanofibrous yarns using two oppositely metallic spinnerets system is presented. This method allows the production of more uniform, stronger twisted poly acrylonitrile (PAN) yarns. The novelty of this system permits for in-situ heat treating of the nanofiber yarns. The average diameter of twisted nanofiber yarns is $340.65{mu}m$ with 5.8 CV%. The values of the initial modulus and stress of heat treated yarns increase from 1.90 GPa and 61.30 MPa in untreated one to 4.51 GPa and 116.56 MPa, respectively. In order to quantify the alignment of the nanofibers Fourier power spectrum (FPS) and image analysis were used. So the treated yarn shows more degree of nanofiber alignments than the untreated one.