Objective According to clinical demand of quantification evaluation on flat-foot and high-arch, to develop an intelligent and rapid method that diagnoses the form of the foot arch based on PCA, and to verify the validity of the system. Methods Choose a group of volunteers with abnormal foot arch and another group with healthy foot arch, implement a system based on plantar pressure measurement to evaluate the foot arch, and verify whether the result is consistent with the clinical diagnose. The Plantar pressure measurement platform is based on a thin-firm piezoresistive sensor array with 44 rows, 52 columns of sensing units and a sampling frequency at 15 Hz. The data is transferred to PC host computer through USB, and the diagnosis and corresponding report are made on the host computer. The above system was compared with the existing plantar pressure acquisition device to verify the precision of collected data. PCA is performed on plantar pressure in order to automatically fit the foot axis, and the result is compared with clinical defined axis. Finally, the method was used for the diagnosis of volunteers with flat foot, high arch foot and normal foot arch to verify the accuracy, each of the 3 groups is consist of 3 volunteers. Results The deviation of the contact area acquired by the system compared to that of an existing plantar pressure acquisition device is less than 3.2%. The angle deviation of the fitted foot axis compared to the clinical defined axis is less than 1°. For 3 groups of volunteers, the system is capable of making a diagnosis that is 92.6% consistent with the clinical diagnosis. Conclusions By introducing the principal component analysis to automatically fit the foot axis, extracted the foot arch from the pressure footprint in a similar way to clinical manual way, developed a quantification evaluation method on form of foot arch and evaluated the validity of the result. The method can be used to assist the clinical diagnosis of flat foot and high arch foot, and help to understand the pathogenesis of foot arch deformity.