Experiment of the fish-shaped phase diagram of the ternary water + octane + 2-butyloxy-ethanol system under atmospheric pressure was performed at constant water/octane mass ratio (1/1) to determine the upper critical solution temperature (UCST= 296.90 +/- 0.05 K) and the lower critical solution temperature (LCST= 286.10 +/- 0.05 K). The liquid-liquid equilibria of the water + octane + 2-butyloxy-ethanol system at 283.15, 293.15 and 303.15 K were measured under atmospheric pressure. At 283.15 and 303.15 K, there is only one two-liquid-phase-coexisting envelop in the triangle phase diagram. At 293.15 K, in-between the UCST and LCST, the system exhibits three two-liquid-phase-coexisting envelops and one three-liquid-phase-coexisting tie triangle in the triangle phase diagram. The experimental results of liquid-liquid equilibria were further correlated with the nonrandom two-liquid (NRTL) model. (c) 2015 Elsevier B.V. All rights reserved.