In this paper, we study the structure effect of dual-spinneret on the fabrication of composite nanofibers with side-by-side heterojunctions in a facile and economic electrospinning technique. Five kinds of dual-spinnerets, which are made of needles, are explored to fabricate composite nanofibers with side-by-side p-n heterojunctions. As representative p-type and n-type oxide semiconductors, CuO and TiO2 are chosen to research the actual result of dual-spinnerets. It is found that the structure of dual-spinneret has obvious effect on the preparation efficiency of side-by-side p-CuO/n-TiO2 composite nanofibers, which can be obtained the highest while a relative curved dual-spinneret is used. The contact area of liquid droplets during electrospinning with different dual-spinnerets is the main reason for producing different heterojunction efficiency. The systematic characterizations, such as X-ray diffraction, field emission scanning electron microscopy, high resolution transmission electron microscopy, are carried out on side-by-side p-CuO/n-TiO2 composite nanofibers. The results provide a guide for preparing other composite nanofibers with side-by-side heterojunctions, which are expected to be used in high-efficiency solar cells, photocatalysts, LEDs, etc.