In this work, the fabrication of the jute fibre reinforced composites are made with the help of the compression moulding technique using the optimum pressure (17 Mpa) along with various fiber dosage (i.e. 0%, 40%, 50%). The optimized condition is obtained for the 40% fiber loading composites in the mechanical properties, then fiber activation is followed by using the NaOH and Ca(OH)(2). The treated fibers composites by adding the copper slag in the range of 0%, 5%, 10%, 15% for the optimized 40% fiber dosage are produced using the unsaturated polyester as matrix. The ejected the specimen is cut as per ASTM to find the mechanical properties such as tensile, flexural and impact. Result revealed that the Ca(OH)(2) treated composite shows better tensile, and impact strength for the 10% copper slag filled composite material and yields higher for 15% for copper slag filled composites in the case flexural strength. Nearly 25% and 22% increase in tensile strength and impact strength was observed for the Ca(OH)(2) treated composite with 10% copper slag inclusion. The 15% copper slag inclusion composite yielded the higher flexural strength. The SEM mechanism revealed the higher mechanical strength for the Ca(OH)(2) treated composite than other composites produced with activated fiber.