The absorption characteristics of optically active constituents (OACs) in water column are important optical properties and key parameters for bio-optical modeling. Inherent optical properties (IOPs) of OACs are mainly determined by three components, i.e., the spectral absorption of non-algal particles, phytoplankton and chromophoric dissolved organic matter (CDOM). Spectral absorption properties, seasonal and spatial variability of particulates (total suspended matters (TSM), including phytoplankton and non-algal particles) and CDOM absorption characteristic were analyzed from water samples collected in May and September 2013, respectively. Compositions of CDOM and non-algal particles were also examined at the same time. The results demonstrated that most absorption curves of the total suspended particulate [a_p(λ)] were similar to non-algal particles absorption [a_d(λ)], showing great variations along the Liaohe River observed at the same time. Significant correlations were obtained between a_p(λ) and a_d(λ), especially the correlations between a_p(440) and a_d(440) (R=0.99 both in May and September). Meanwhile, strong relationships between a_p(λ) and the absorption of phytoplankton [aph(λ)]were exhibited at 675 nm, with correlation coefficient (R)=0.81 in May and R=0.55 in September, respectively. Moreover, close relationships between a_p and TSM at both 440 and 675 nm were revealed while significant correlations were obtained between a_p(675) and chlorophyll a (Chla) for samples collected in both seasons. According to our investigation, no significant relationships were exhibited between a_p(λ) and dissolved organic carbon (DOC). A close relationships between a_p(λ) and inorganic suspended particulate (ISM) and organic suspended particulate (OSM) were recorded in September, while it was not the case for samples in May. Significant correlations were also yielded between CDOM and DOC concentration for samples collected in September (R=0.90) at 440 nm, which was higher than that in May (R=0.55). Moreover, content of mineral particulates in Liaohe River was higher than most other water bodies based on the analysis of slopes of non-algal particles absorptions. The composition of auxiliary pigments and Chla concentration in phytoplankton showed small seasonal variations but great spatial variability as indicated by the ratio of a_ph(440)/a_ph(675). Furthermore, absorption characteristics of CDOM exhibited similar curves with non-algal particles, however showed great variability among different sampling sites. In addition, CDOM absorption slopes (S_CDOM) of the Liaohe River, though exhibiting greatly spatial variations, were smaller than other water bodies, which indicated that the CDOM composition of Liaohe River was inclining to have high molecular weight. Our investigation indicated that the total particulate absorption was dominated by the non-algal particles at 440 nm both in May and September. The average contribution rate of non-algal particles is 67.46% in May, while for 97.5% of water samples, the contribution rate of non-algal particles reaches up to 50% in September. Consequently, contribution rate of non-algal particles at 440 nm in September was higher than that in May for the high precipitation while contribution rate of a_CDOM(440) was litter higher than that of a_ph(440) in both months.