Nanofiber core-spun yarn (NCSY) combines the advantages of traditional fibers and nanofibers to be widely used in smart wearable textiles, biomedical textiles, and functional textiles. Here, for the first time, the forming process of NCSY and its shape regulation mechanism were explored via finite element analysis and response surface analysis method to obtain mathematical model for predicting the various forms of yarn. As proof-of-concept applications, shape-controllable nanofiber core-spun yarns were prepared for thermal–moisture management and solar steam generation, respectively. The as-obtained shape-controllable PAN nanofiber/cotton composite yarns could achieve an interval control of average water transfer velocity in the horizontal (0.17–0.24 cm min-1) and vertical (0.24–0.33 cm min-1) directions within 30 min due to the arrangement of PAN nanofibers causes microchannels and hydrophilicity, matching the sweat secretion of human bodies under dynamic or static conditions and realizing the purpose of thermal and moisture comfort. Furthermore, PAN nanofiber wrapped CNTs/cotton composite yarn-based (PAN@CNTs-NCSY) evaporator was designed, which shows a fast water evaporation rate of 1.40 kg m-2 h-1, exceeding in most fabric-based evaporators reported to date. These findings have guiding significance for preparing rich style NCSY according to demand and designing functional and intelligent textiles via adjusting the type of core and shell fibers.