In order to solve the reconstruction of extremely incomplete data under the condition of limited viewing angles in optical computerized tomography (OCT), the orthogonal projection sampling method is proposed to reconstruct the threedimensional flow field containing shield by the least projection direction components with the prior knowledge algorithm based on modified algebra reconstruction technology (ART). With the numerical simulation of computer, the incomplate data reconstruction precision and meansquare error of threedimentional flow field containing shield are discussed under the condition of limited viewing angles. The results indicate that the orthogonal projection sampling method can greatly reduce the error and improve the precision in the reconstruction of extremely incomplete data for the threedimensional flow field containing shield within limited viewing angle, and this work provides an important reference for the practical measurement of incomplete data with OCT.