Abstract: Standing traveling wave boundary condition (STWBC), clear in concept and easy t o implement, is a newly proposed absorbing boundary condition. In this paper, th e STWBC is discussed again according to its errors and limitation in application . It is proved that the basic theory of the novel STWBC is correct; the only que stion is how to reduce the differential error when applying the STWBC. At the sa me time, the error mechanisms of the original one order iterative equation for STWBC are analyzed theoretically in one dimensional and two dimensional spaces respectively, and a second order iterative equation is put forward.