The aliphatic poly(lactic acid)/poly($varepsilon$-caprolactone)(PLA/PCL) blends for bioabsorbable filament sutures were prepared by melt blending. The ester interchange reaction by alcoholysis between two polymers was studied. Also, their thermal properties and miscibility changes due to the alcoholysis were investigated by FT-IR, $^1H-NMR$ and DSC analyses. It was found that PLA/PCL random copolymers have been formed during the melt blending through the ester interchange reaction by alcoholysis. The optimum blending conditions for this reaction were determined. The thermal properties of PLA/PCL blends such as melting temperature and heat of fusion were decreased with increasing interchange levels. However, the miscibility between two polymers was improved greatly by the ester interchange reaction.