A new phenomenon about {111} planar particles blocking dip in Si has been found. Between the {111} planes in single crystal Si there are two interplanar spacings, d(111)(a) and d(111)(b), but there is only one interplanar spacing d(110) between Si{110} planes, so that their blocking dips would be different. We have observed this difference from the experiments of a particle and proton blocking effect in single crystal Si. We have also estimated the 2ψ1/2 angles from planar particles blocking dips with d(111)(a), d(111)(b) and d(110) in Si respectively. According to the author's knowledge, up to the present, this phenomenon has not yet been discovered at home and abroad. This new phenomenon will promote the study of complex crystals using the blocking and channeling effects.