A straight trajectory CT device can be used in radiation imaging. The device includes: a ray-generating unit that generates a ray within a specific range of field angle; a channel for an object to be inspected though which the object to be inspected passes; a first collimator; and a ray receiving unit provided on both sides of the channel for the object to be inspected. The ray beam is received by the ray receiving unit after penetrating the first collimator and the object to be inspected in order. The ray generating unit is static and the first collimator moves in the same direction as the ray receiving unit. This direction is parallel to the channel for the object to be inspected. The device can complete computed tomography with a minimum of one ray receiving unit, thereby simplifying the structure of the device and reducing its cost.