This paper adopts the phase-field based lattice Boltzmann (LB) method to study the dynamic behavior of soluble surfactant-laden droplets in a uniform electric field. Firstly, two benchmark problems including the surfactant concentration distribution of static droplet and the deformation of leaky dielectric droplet in an electric field, are used to test the capacity of LB method. Then, we focuse on investigating the deformation, breakup, and coalescence behaviors of surfactant-laden droplets in an electric field. The results show that: (1) For the deformation behavior, the single droplet exhibits two distinct deformation modes: prolate and oblate shapes. Higher electric capillary number and bulk surfactant concentration both lead to greater droplet deformation. (2) For the breakup behavior, the single droplet exhibits two distinct breakup modes: filamentous and conical jetting breakup. The droplet with surfactants is more like to breakup. More specifically, surfactants reduce the retraction degree of the main droplet after filamentous breakup, while it increase the number of satellite droplets formed at the main droplet ends after jetting breakup. (3) For the coalescence behavior, the double droplets exhibit two distinct processes: deformation coalescence and attractive coalescence. A higher electric capillary number facilitates droplet coalescence. Surfactants promote deformation coalescence while retarding attractive coalescence, but the promotional effect dominates. Consequently, a higher bulk surfactant concentration enhances the propensity for the droplet coalescence.