<p>Composite fibers have attracted significant attention due to their distinctive structural properties and performance characteristics. Currently, the focus of research lies in innovating composite spinning technology and optimizing mechanism parameters. Among these techniques, rotary jet spinning has emerged as a notable method for cost-effective and high-speed production of composite fibers. Rotary jet spinning utilizes centrifugal force to stretch two polymer solutions from a composite droplet into a composite jet, with this morphological transformation occurring within the micro-triangle. The continuous and stable stretching motion within the micro-triangle directly influences the velocity distribution and flow stability of the composite solution, ultimately impacting the morphology and quality of the resulting composite fibers. This article presents the utilization of a rotary jet spinning device for fabricating composite fibers. It provides an in-depth analysis of the cone formation mechanism in composite spinning solutions and establishes a theoretical model for micro-triangle motion. The flow field of the micro-triangle is simulated using finite element simulation software, investigating how rotation speed and solution concentration impact PEO/PVP composite fiber morphology. Experimental results validate both theoretical modeling accuracy and numerical simulation, demonstrating that adjusting relevant parameters can control composite fiber morphology and structure.</p> Graphical abstract <p></p>