Gap characteristics were studied in the mixed broad-leaved Korean pine forest in Xiaoxing'an Mountains. The results showed that the linear gap density in the forest was 31.78 gaps/km. The canopy gaps and expanded gaps occupied 15.71%, and 30.78% of total investigated area, respectively. The yearly gap disturbance frequency was 0.46% and the disturbance rotation was 434.8 years. Canopy gaps varied from 42.12 to 372.52 m² and average area of canopy gaps was 153.37m². Expanded gaps varied from 98.65m² to 633.10m² and average area of expanded gaps was 300.44m². The distribution pattern in both canopy gap area and expanded gap area followed Weibull model. The major means of gap formation was breakage at base(35.29% of the total), and the second was uprooting (28.43%).The average number of gap makers was 4.98 per gap. Major gap makers were Pinus koraiensis, Betula platyphylla, Abies nephrolepis, Betula costata, of which the diameter at breast height (DBH) were between 20-30 cm and the height ranged from 15 to 30 m. For canopy gaps, their distribution in relative frequency of the ratio of their diameter to the height of forest gap (d_CG/H) presented single peak curve, the peak value occurred when the ratio of d_CG/H was between 0.30-0.45, but for expanded gap, their distribution exhibited double peak curves, the peak value came when the ratio of d_CG/H was between 0.75-0.90 and between 1.05-1.15, respectively, in the mixed broad-leaved Korean pine forest in Xiaoxing'an Mountains. The distribution of DBH classes and tree height classes of gap border trees followed Weibull distribution model but they did not follow the normal distribution model. About 13.41% of GBT had regular crowns, the GBT, of which the ratios of crown inclination (RCI) ranged from 0.5 to 0.7, comprised about 70.49% of total GBT.