There are lots of duplicative components in the glyph blocks of Maya hieroglyphs. Some of them are used to double the meaning or sound value of the original components. Some of them are just the aesthetic consideration of scribal which does not affect the significance of the original components. This phenomenon, which was discovered by earlier Maya epigraphers, still needs researches on its causes and substitution patterns. This essay discussed these two issues based on the rearrangement of the glyph blocks containing duplicative components. From the perspective of graphic structure, the doubling phenomenon existed in both syllabic signs and glyphs. There are two reasons for the doubling phenomenon as such. The redundancy and simplification of signs lead to the sign-internal duplication. The unique spelling rule of Mayan language lead to the repetition of the syllabic signs. From the perspective of glyphs, the doubling phenomenon existed in both compound graphs and couplets which are caused by the recombination of glyphs. The substitution patterns of these phenomenon are the use of doubling signs, underspelling, choosing different variants of the same syllabic sign, and sharing components. All of these four substitution patterns can function both in the glyph-internal and between different glyphs.