Spin-transport properties of in-plane fluorinated zigzag (8, 0) single-walled carbon nanotubes contacted by two CrO2 Half-Metallic-Ferromagnetic (HMF) electrodes are investigated using density-functional theory. Comparison of the results with pristine carbon nanotube show that fluorinated carbon nanotube (CNT) offers high TMR similar to 100 % and the transport phenomenon is tunneling, since there are no transmission states near Fermi level. However, for pristine CNT structure the transport phenomenon cannot be tunneling since there are significant number of transmission states near Fermi level, although high Magneto Resistance (MR) similar to 97 % is observed in it. Both TMR and Spin Injection Efficiency eta (Spin-Filtration) are higher in fluorinated (8, 0) carbon nanotube (CNT) structure, which is due to fluorinated carbon nanotube (CNT) acting as a perfect barrier in vertical (out-of-plane) arrangement resulting in negligible spin-down current (I down arrow) in both Parallel Configuration (PC) and Antiparallel Configuration (APC).