The samples of dead wood (the pine, spruce, fir, cedar), damaged in 2017 by the siberian silkmoth and cedar-tree borer is displayed at April 2022 on the Yenisei region of Krasnoyarsk Territory with for sulphate delignification, optimization of the cooking process, estimation of the unbleached cellulose characteristics, determination of the possibility of its use as fibrous semi-finished product of cellulose-paper production. The sulphate cookings are executed in laboratory autoclave under the following constant conditions: hydromodule 4.8; the degree sulfiditiy of the cooking solution 20.8%; the temperature 170 °C. In the course of experiment varied the active alkali consumption (15.5–18.5% from wood mass in unit Na2O) and duration of the isothermal cooking (4.5–6.5 hours). The dependencies of the output and of the cellulose characteristics from these factor is approximated by the regression equations of the second order. Mathematical model of the cookig process obtained such way is used for graphic presentation result in type of the three-dimensional surfaces of the response and for calculation of the best values of the variable cooking factor: consumption active alkali 16.2%; cooking duration 6.1 hour. All samples of the wood was be cooking separately on optimal regime. The cooking results: the cellulose output 37.9–41.3%; the no-cooked part less 1%; degree of the cellulose delignification 23–29 Kаppа unit (the mass part of the lignin 3.38–4.21%); the explosive length 8130– 9250 m; the forcing through resistance 400–490 кPа; tearing resistance 630–870 mmN; break resistance 380–460 bends. The characteristic of the all cellulose samples answer to the mark NS-3. It is noted significant reduction of the cellulose output (on 10–2%) in comparison with cellulose similar degree delignification from sound wood.