The invention is related to the field of pharmaceutics, in particular, to an anti-tumour pharmaceutical composition comprising temozolomide, and can be used in medicine, in particular, in oncology. The objective of the invention is provision of an anti-tumour pharmaceutical composition comprising temozolomide that features high efficiency, improved stability, provides high accessibility of tumour cells for the anti-tumour agent, and development of a method for producing such composition. Said objective is attained by provision of a sustained-action anti-tumour pharmaceutical composition for treatment of oncological diseases including temozolomide and pharmaceutically acceptable excipients, characterized in that the composition contains, as pharmaceutically acceptable excipients, polysaccharide phosphates in salt and acidic forms with the following contents of the components, wt.% : temozolomide - 5-20, polysaccharide phosphate - 30-80, polysaccharide phosphates in the acidic form - up to 100.