Purpose: By virtue of a stereotactic head frame (SHF), stereotactic radiosurgery is considered one of the precisest treatments. Several studies, however, presented the SHF could be bent and/or displaced due to weight-bearing to the frame and/or patient position change, which might cause significant inaccuracy up to 6 mm in certain circumstances. Nevertheless, to our best knowledge, no clear mechanism of SHF QA has been established. We are under development of a stereo-camera-based QA system for SHF to check its integrity of shape and placement. In this preliminary study, a prototype of camera system was developed and its reliability and accuracy were evaluated. Method and Materials: The prototype of camera system consists of two CMOS (complementary metal oxide semiconductor cameras) and a control computer. It was designed to measure 3D coordinates of points from left-right image pair through calibration and triangulation. A software program was written in C for system operation and image reconstruction. For reliability test, six image pairs of a fixed circle-pattern were obtained every 5 minutes for 25 minutes. Then, the vector of each circle's center was calculated between the first- and n-th image pair. To evaluate accuracy, sets of image pair for translation and rotation were obtained. Then, differences in translation and rotation from the reference were calculated using singular value decomposition. Results: The camera system showed reliability of within 0.5mm during 25 minutes. The accuracy was within 1 mm in translation and 1° in rotation. Conclusion: The prototype of stereo camera system developed in this study demonstrated its potential of being applied for SHF QA. The study will be continued for further evaluation and improvement.