In the carbon-nanotube study field, Young's modulus is of prime significance, as it needs to be put into all CAE softwares when we like to analyze, design, or even manufacture a device made up of carbon nanotubes. It seems that, however, no authors devoted their efforts to the investigation of the effect of thickness, diameter, chiral angles, and bond angles especially on Young's modulus for chiral carbon nanotubes. This paper, thus, will examine the effects above closely and thoroughly and from the related figures shown can we find distinctly the correlation among them. It should be stressed here that, when the impact of bond angles on Young's moduli is taken into account, the precise values of them can be obtained.