Objective To observe the morphology and variation of foramen ovale (FO) and provide reference for the diagnosis and treatment of trigeminal neuralgia and cavernous sinus tumors. Methods Totally 83 adult dry skulls were examined with a sliding caliper. The lengths and widths of the FO, distances between the FO and apex partis petrosa (FO-APP) and distances between the FO and posterior clinoid process (FO-PCP) were measured in an intracranial view of the skull. Results ①The FO displayed a shape of ovale in 98 cases, “D” in 60 cases, triangular in 3 cases, round in 2 cases, irregular in 2 cases and slit in one case. The bony spine was found in 3 cases, bony tubercle in 3 cases and bony spur in 2 cases. ② In the left side, the length and width of FO were (7.37±1.21 mm) and (4.28±0.99 mm); distances of FO-APP and FO-PCP were (9.88±3.54 mm) and (15.68±3.49 mm). In the right side, the length and width of FO were (7.84±1.18 mm) and (4.06±0.99 mm); distances of FO-APP and FO-PCP were (9.44±3.20 mm) and (16.74±4.57 mm). ③ There was statistical significance between the lengths of both sides (P < 0.05). There was negative correlation between the width of the FO and FO-APP in the right side, FO and FO-PCP in the right side, and the FO and FO-APP in the left side (r = -0.341, r = -0.369, r = -0.526, P < 0.05). Conclusions The analysis of FO, petrous apex of temporal bone, posterior clinoid process and other important structural and anatomical parameters not only improves the understanding of the anatomical characteristics of the middle cranial fossa, but also has important significance in the diagnosis and treatment of trigeminal nerve decompression and cavernous sinus tumors.