The invention discloses a detection tool and a detection method for the position of a cylinder head process hole. The detection tool comprises a test board, a tubular locating test sleeve, a locating block, a process hole round locating rod, a process hole diamond locating rod, three or more intake valve seat blank hole diamond pins and a scanning gauge, wherein the test board is provided with a test through hole corresponding to the to-be-detected process hole on the cylinder head and intake valve seat blank holes; and the locating block is fixed on the lower surface of the test board; the locating test sleeve and the test through hole are coaxially installed on the upper surface of the test board, and diameters of inner holes are larger than those of the corresponding intake valve seat blank holes. Whether a round ring in the locating test sleeve corresponding to the intake valve seat blank holes is large on one side and small on the other side can be observed through visual inspection, the specific amount of deflection can be detected through the scanning gauge, and modes can be selected as required in production; and the detection tool and the detection method are convenient, rapid and high in measuring accuracy and detection efficiency.