Uncertain parameters exist in complex structures, such as the cervical spine, and they may produce unexpected significant influences on the structures. Therefore, for an accurate injury analysis of the cervical spine, it is essential to consider the uncertainties contained in the cervical spine components. For this research, motions segment of finite element C5-C6 motion segment was created and validated based on experimental data under various loading conditions. Young's moduli of the cervical spine components were considered random variables. Then, based on the sensitivity analysis, Young's moduli of the disc annulus and nucleus were considered random fields. Each random field was discretized into three and four sets of random variables for the disc annulus and nucleus, respectively. Using sets of random variables discretized from a random field, the sensitivities of the sensitive parameters were reduced to less than 0.05, in which the randomness may be ignored without losing analysis accuracy. The variance for probabilistic injury function was also decreased after random field analysis procedure. Moreover, considering material properties to be a random field, the reliability also increased. Reliability increased by 12.69% when Young's modulus of both the disc annulus and nucleus were considered random fields.