The unified evaluation method of spatial straightness deviation in Cartesian coordinate system has not been established at present. For the situation, an evaluation method of spatial straightness deviation in Cartesian coordinate system based on point features is proposed in this paper. Using the relationship between the spatial straightness deviation measurement model and the point characteristics, and based on the spatial straightness measurement method in Cartesian coordinate system, the mathematical models for the spatial straightness deviation evaluation in Cartesian coordinate system are established. On the basis of the cross-section measurement method, the measurement model of spatial straightness deviation is established. Based on the mathematical equation of arbitrary symmetric quadratic curves in space, the least square measurement section profile curve is constructed to solve the problem of obtaining the center of the measured section profile. Finally, the accurate evaluation of the spatial straightness deviation is realized according to the point characteristic relationship. Moreover, the rationality and accuracy of the proposed method are verified through practical tests, which provides a strong support for promoting the development of spatial straightness measurement technology.