Single additive optimization experiments were conducted for the design of the binary mixed additives (BMA). Effectiveness of the BMA on the FO performance was extensively evaluated and confirmed. ZnCl2-LA enhanced both water flux and salt rejection by ~51.3% and ~8.1% compared to HTI CTA membrane, respectively. BMA significantly improved the water flux more than three times compared to the membranes with single additives. Trade-off effect between the selectivity and permeability was partially broken for our membranes with BMA.