The conversion of lignocellulosic biomass to bioethanol has attracted renewed attention in recent years due to its environmental, economic, and strategic advantages. Birch woodchips were used as the raw material due its several characteristics, such as high cellulose and hemicellulose content that can be readily hydrolyzed into fermentable sugars. Dilute acid hydrolysis was used as the pretreatment process which can be considered as one of the most promising biomass pretreatment methods. But there occur several challenges and limitations in the process of converting birch wood to bioethanol. During the biomass pretreatment process the degradation products such as furfural and acetic acid, which has an inhibitory effect on the further fermentation process in the bioethanol production section, may be form from hemicelluloses. But both these inhibitors as individual chemicals are very important for the production of many products. In order to develop the theoretical foundations for joint production technology of furfural, acetic acid and bioethanol, it is necessary to study the effect of the amount of catalyst on the formation of furfural and acetic acid from birch woodchips and the content of cellulose in the lignocellulose residue after pretreatment process. The effect of the amount of the catalyst on the furfural and acetic acid formation process was studied in a range from 1.5% to 4.0%, calculated on oven dried wood (o.d.w.), while temperature and time of the pretreatment process were constant. The obtained results demonstrated that the effect of the amount of the catalyst on the formation of furfural and acetic acid and the content of cellulose in the lignocellulosic leftover is very significant. The amount of furfural increased from 6.2 % to 10.8%, calculated on o.d.w., the amount of acetic acid increased from 5.2% to 5.8%, calculated on o.d.w., but the content of cellulose in the lignocellulosic leftover decreased from 34.7% to 14.1%, calculated on o.d.w. after 90 min from the beginning of the birch wood pretreatment process.