Ferreiro work (1988) suggests that children's knowledge of written language evolves in a process that essentially takes place on three levels. Same consistency about these levels were found in Portuguese (e.g. Alves Martins, 1996; Silva, Almeida & Alves Martins, 2012). Molinari and Ferreiro (2009) found that attempting to write the same words in different moments preschool children establish different correspondences between oral and written units. The authors (2009) analyzed the graphic stability of invented writing when preschool children had to handwrite and type down on a computer the same list words and were not authorized to consult their previous version. The results indicate that children only maintain graphic stability (mobilization the same letters to represent the same syllable of the word) of invented spelling when they began to use conventional letters in their writing (at a syllabic level or at an alphabetic level). The aim of our study was to compare children invented spelling in two consecutive moments, using the methodology proposed by Molinari and Ferreiro (2009), and understand how graphic stability of invented spelling evolved in Portuguese preschool children. The Participants were 90 preschool children of a middle-high socio-economic level divided in 3 groups (n=30) per the nature of their invented writing (G1 - Syllabic with phonetisations; G2 - Syllabic - Alphabetic; G3 – Alphabetic) and all were equivalent at age, intelligent level and letter known. The methodology used consisted in asking children to write down a shopping list (only composed by common names) first manually and then they should type down the same list without seeing how they wrote the words before. We classified the pairs wrote as total identity (pairs were children used the same letters in both attempts), Partial Identity (pairs were one of the letters was the same and the other were different) and graph-phonetic alternations (pairs were children used different letters with correct phonemic value in each word). The results indicate that the presence of the keyboard with all the letters it seems to be a facilitator to more correct phonetisations. We also found at the comparison of pairs of invented spelling that exists a strong presence of pairs with graph-phonetic alternation in participant's syllabic-alphabetic spells. These graph-phonetic alternations have considerable theoretical interest in understanding the evolution of children's knowledge of the written language, because in shows that the stabilization of the alphabetic principal it´s no linear or result of more correct phonetisations.