UHMWPE fibers were dyed with a series of anthrquinoid blue dyes having different length of alkyl substituents at general dyeing condition. The dyeability was investigated at various conditions and fastness of the dyeings was examined. As the length of alkyl substituents increased, the dyeability toward UHMWPE fibers tends to be improved gradually. Color strength of the fabrics was increased with the increase of dyeing temperature from 100 to $130^{circ}C$. From the dyeing rate, equilibrium dyeing at $130^{circ}C$ was achieved at 2-3 h. The tensile strength of UHMWPE fibers after dyeing at $130^{circ}C$ for 1 h was maintained at a level of 95 % of untreated fiber. However, at prolonged dyeing time at $130^{circ}C$, the tensile strength was significantly decreased to a practically unacceptable level. The color fastnesses to washing, rubbing and light of the dyeings were very good showing higher than 4 ratings.