Break-up behaviors and mechanism of oil-in-water emulsion droplets at the restricting element in the pipeline flow were investigated by experiments. The results show that that the break-up of droplets mainly occurs in the near wall region and downstream of the circular orifice, and the break-up probability is an increasing function of the ratio between the available amount of turbulent stress acting on the droplets and their surface energy, and also an increasing function of the Weber number based on the maximal pressure drop through the orifice. In the turbulent pipe (Re>4000), oil droplets fully oscillate and gain more velocity gradient, shear force and inertia force, being easy to break up. The interfacial tension of Red Sudan IV colored n-heptane system has the value of 23.6 mN/m, decreasing from 47 mN/m without its coloring, the function of viscous force on the break-up of droplets decreases, but the function of inertia force caused by flow velocity and pressure drop is dominant, leading to stronger action on the break-up of droplets. The flow velocity, governed by the flow rate and restriction ratio, controls the turbulent shear force on the dispersed phase oil droplets. Larger injected volumes of n-heptane (0.5~5 mL) weaken the function of the orifice on the break-up of droplets, and the two-phase system tends to generate bigger diameter daughter-droplets with the median diameters from 20 to 35 mm.