In order to reduce the pectin content (mass fraction) in reconstituted tobacco, the degradation conditions of tobacco stem end mixture from defiber and extraction during paper-making reconstitution process by pectinase from Aspergillus niger were optimized by single factor and orthogonal experiment methods. The pyrolysis products were investigated by on-line pyrolysis gas chromatography / mass spectrometry (PY—GC/MS) prior to and after enzymolysis. The monosaccharide composition of pectin prior to and after enzymolysis was analyzed by silanizing GC/MS. And sensory evaluation was investigated by adding the degraded tobacco sample into cigarette. The results showed that: the optimal reaction conditions of pectin degradation were: the enzyme activity 3 700 U/mL, the ratio of liquid to solid 1︰1 (m︰V), temperature 50 ℃, time 1.5 h. Under this conditions, the pectin degradation rate was 32.47%. After enzymolysis, the contents of glucose and galacturonic acid in the monosaccharide composition of pectin were decreased. The composition and content of pyrolysis of tobacco samples also changed obviously. Compared with the control, the phenol content was reduced from (3.00±0.16)% to (2.46±0.11)%, and the flavor contents of aldehyde ketones and alcohols was decreased while heterocyclic and ester aroma substances were increased. Sensory evaluation showed that after the enzymatic samples were added to the cigarettes, the smoke of the cigarettes became softer with better permeability, and the irritation was reduced, but the amount of aroma was slightly become less and strength was insufficient.