The invention discloses parallel composite elastic fiber and a manufacture method thereof. The parallel composite elastic fiber is obtained through false twisting process after parallel composite spinning of valox and polyethylene glycol terephthalate according to a weight ratio of 70/30 to 30/70, wherein the inherent viscosity of the valox is between 0.45 to 0.60 dl/g, and the difference of the inherent viscosity of the valox and the inherent viscosity of the polyethylene glycol terephthalate is between 0.40 and 1.05 dl/g. The elastic extensibility of the elastic fiber of the invention is between 130 and 220 percent, and the elastic recovery rate is higher than 85 percent.