A method for sulphation and phosphorylation of a cellulose substrate to impart anti-flame properties to the cellulose substrate comprising the following operations: i) provide a cellulose substrate; ii) prepare a sulphation and phosphorylation solution, preferably under heated condition, the sulphation and phosphorylation solution comprising water, ammonium sulphamate, urea and at least one compound of formula: PO 2 -R-PO 2 wherein R represents a linear or branched, substituted or unsubstituted C 1-10, preferably C 1-5, alkyl group; a N(R 1) group; a R 2 N(R 3)R 4 group; R 1 represents H, a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; R 2 and R 4 represent independently a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; R 3 represents a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; a R 5 N(R 6)R 7 group; R 5 and R 7 represent independently a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; R 6 represents a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; a R 8 N(R 9)R 10 group; R 8, R 9 and R 10 represent independently a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; with the proviso that the number of -PO 2 groups in the general formula is not greater than 5; iii) immerse the cellulose substrate in the sulphation and phosphorylation solution; iv) extract the cellulose substrate from the sulphation and phosphorylation solution; v) maintain the cellulose substrate at a temperature comprised between 110° and 175°C for a period of time comprised between 1 minute and 3 hours, obtaining at the end a sulphated and phosphorylated cellulose substrate with anti-flame properties. i) provide a cellulose substrate; ii) prepare a sulphation and phosphorylation solution, preferably under heated condition, the sulphation and phosphorylation solution comprising water, ammonium sulphamate, urea and at least one compound of formula: PO 2 -R-PO 2 wherein R represents a linear or branched, substituted or unsubstituted C 1-10, preferably C 1-5, alkyl group; a N(R 1) group; a R 2 N(R 3)R 4 group; R 1 represents H, a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; R 2 and R 4 represent independently a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; R 3 represents a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; a R 5 N(R 6)R 7 group; R 5 and R 7 represent independently a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; R 6 represents a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; a R 8 N(R 9)R 10 group; R 8, R 9 and R 10 represent independently a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; with the proviso that the number of -PO 2 groups in the general formula is not greater than 5; R represents a linear or branched, substituted or unsubstituted C 1-10, preferably C 1-5, alkyl group; a N(R 1) group; a R 2 N(R 3)R 4 group; R 1 represents H, a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; R 2 and R 4 represent independently a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; R 3 represents a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; a R 5 N(R 6)R 7 group; R 5 and R 7 represent independently a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; R 6 represents a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; a R 8 N(R 9)R 10 group; R 8, R 9 and R 10 represent independently a linear or branched, substituted or unsubstituted C 1-5, preferably C 1-3, alkyl group; iii) immerse the cellulose substrate in the sulphation and phosphorylation solution; iv) extract the cellulose substrate from the sulphation and phosphorylation solution; v) maintain the cellulose substrate at a temperature comprised between 110° and 175°C for a period of time comprised between 1 minute and 3 hours, obtaining at the end a sulphated and phosphorylated cellulose substrate with anti-flame properties.