Leaf area index (LAI), defined as the total one-sided leaf area per unit ground surface area (m²m^-2), is among the most frequently used parameters for analysis of plant canopy structure. Most ecosystem process models that simulate carbon and water cycles at a stand or regional scale require LAI as an input variable, thus accurate measurement of LAI is essential for conversion of leaf-level processes to the canopy level. The main methods of LAI measurement generally are classifiable into two groups: direct measures, which mainly include destructive sampling and the litterfall method; and indirect measures, which mainly include hemispherical photography and the LAI-2000 plant canopy analyzer. However, using a direct or indirect method alone may not accurately estimate LAI for mixed needle and broadleaf forest or broadleaf forest with a high proportion of evergreen species. Secondary Betula platyphylla is among the most common broadleaf forest types that regenerate naturally after clear cutting of broadleaved-Korean pine forest in the Xiaoxing'an Mountains in north-east China. In the present study, we estimated LAI and its seasonal dynamics in secondary B. platyphylla forest in the Xiaoxing'an Mountains using optical methods (hemispherical photography and the LAI-2000 Plant Canopy Analyzer) and a combinational method (hemispherical photography combined with the litterfall method). In the combinational method, hemispherical photographs obtained in early November were calibrated with consideration of the woody-to-total ratio (α) as well as the clumping index (for clumping beyond the shoots, Ω_E). The calibrated value was regarded as the true LAI (LAI_t) of coniferous species; the LAI_t of the study stand and its seasonal dynamics (from July to November) were obtained by supplementation of the LAI_t of coniferous species by incorporation of litterfall data for each observation. Using this result as a reference value, we compared the results obtained with the two optical methods. The LAI for the litter of B. platyphylla and Larix gmelini accounted for 87.65% of the total litter, and leaves of B. platyphylla began to fall distinctly earlier than those of other species, and the LAI for the litter of B. platyphylla accounted for 98.24% of all species during July and August. Leaf fall for most species excluding B. platyphylla peaked in mid-September. In contrast to the proposed method, hemispherical photography and LAI-2000 both underestimated LAI by 2.83% and 6.20%, respectively, during the maximum LAI period and overestimated LAI significantly on average by 118.13% and 89.34%, respectively, on other dates. However, hemispherical photography and LAI-2000 yielded LAI values that were significantly correlated with the results obtained with the combinational method; the regression curves were LAI_t= -1.1393 + 1.0934·LAI_HP (R²= 0.80) and LAI_t= -0.1712 + 0.6259·LAI_LAI-2000 (R²= 0.83), respectively. The corrected hemispherical photography data were used to simulate the seasonal dynamics of LAI from May to November, which was indicated to be accurate (R²= 0.87). The LAI estimate obtained with the two optical methods did not differ significantly from July to September, but the estimate with the LAI-2000 method was significantly lower than that obtained with hemispherical photography after October. However, LAI estimated with the two optical methods was significantly correlated (R²= 0.86) for secondary B. platyphylla forest. This study lays a foundation for convenient, rapid and accurate estimation of LAI for secondary B. platyphylla forest in subsequent studies.