Graphs of the two sets of data are "very, very simliar," the person said on Monday, asking not to be identified because the matter is still in the early stages of investigation.
The angle is a key flight parameter that must remain narrow enough to preserve lift and avoid an aerodynamic stall.
A flight deck computer's response to readings from an apparently faulty angle-of-attack sensor is at the centre of an ongoing probe into the Lion Air disaster.
The similarity between the two data readings on the Ethiopian and Lion Air flights will be subjected to further investigation, the person said.
Ethiopian and other investigators were not immediately available for comment.