PURPOSE: To obtain the subject composition low in viscosity even in the presence of a functionality-imparting agent, excellent in meterability, comprising a carbodiimide compound and at least one kind selected from polybutadiene-based dispersants and hydrogenated polybutadiene-based dispersants.

CONSTITUTION: This composition comprises (A) 100 pts.wt. of at least one kind of dispersant selected from polybutadiene-based dispersants and hydrogenated polybutadiene-based dispersants and (B) pref. 1-130 pts.wt. of a carbodiimide compound of pref. the formula (R1-R2 are each a 1-6C alkyl; R5-R10 are each H or a 1-16C alkyl) (e.g. 2,6,2',6'-tetraisopropyldiphenylcarbodiimide). The component A is pref. liquid at normal temperature. This composition is homogeneously mixed with a thermoplastic resin (e.g. a polyester resin) followed by melt spinning to obtain uniform fibers.