The Shitoukoumen Reservoir, an urban water resource of Changchun City, was chose as a represent case of waters in Northeast of China, and then its spectral absorption properties of particulates were analyzed using the field data on June 13th and September 23rd 2008, respectively. Results showed that the content of total suspended matters (TSM) was higher but content of chlorophyll-a (Chl.a) was lower in June than that in September. The spectral curves of TSM were similar to that of tripton. Tripton contributed much more than phytoplankton in the absorption by TSM. In September, the contribution coming from phytoplankton slightly increased, which resulted in an obvious absorption peak around 440nm in the spectral absorption curves of TSM. Absorption by tripton at 440nm had a good relationship with TSM but not with Chl.a. The absorption of phytoplankton in Shitoukoumen Reservoir was generally low. Chl.a held the majority of the pigment composition and had good exponential relationships with its absorption at 440nm and 675nm, respectively. The average values of phytoplankton specific absorption coefficient at 440nm and 675nm in June were 0.0483m²/mg and 0.0263m²/mg respectively, while the data in September were 0.0337m²/mg and 0.0187m²/mg respectively.