Recently developed crystalline polycycloolefins (c-PCO) are attracting attention as a new type of engineering plastics due to their high thermal and chemical resistances. In our previous study, high-speed melt spinning of a c-PCO (Tg: 95 oC, Tm: 263 oC) was conducted, and the occurrence of orientation induced crystallization above take-up velocity of 4 km/min was confirmed. However, the as-spun c-PCO fibers only exhibited low crystallinity because of the limited spinnability and the development of radial structure variation in the fiber cross-section. With the aim of enhancing the structure development of c-PCO fibers, two methods were adopted in this research: the sheath-core bi-component spinning with another polymer and the annealing of as-spun fibers. Enhancement of the orientation development of c-PCO was found to occur through the bicomponent spinning with polyesters. The highest birefringence of c-PCO component was achieved through the bicomponent spinning with poly(ethylene terephthalate) (PET) at 4 km/min with the sheath-core composition of PET:c-PCO=2:1. Further increase of take-up velocity caused the significant suppression of fiber structure development in c-PCO because of the preferred crystallization of PET component in the spin-line. Birefringence of the as-spun c-PCO fibers increased significantly after annealing, i.e. with an increase in the crystallinity, whereas the birefringence of high-speed-spun fibers was quite low in comparison with the drawn fibers of similar level of crystallinity. It was speculated that there are two stable molecular conformations, i.e. contracted and extended ones, with the extended one in the crystalline unit cell. During the heating process of as-spun fibers under free-state, birefringence once relaxed to zero above the glass transition temperature, and then started to increase with further increase of temperature, suggesting the existence of highly elongated net-work structure even though birefringence of as-spun c-PCO fiber is quite low.