The electric spring (ES) is a kind of electric device used for energy buffering, based on voltage and power management. ES transfers the voltage (or energy) fluctuation in the main bus to the non‐critical load (NCL), stabilises the main voltage for critical load, and actively adjusts the power consumption of the NCL to achieve regulation goals of distribution network with wide voltage operational range of NCL. With lots of intermittent and fluctuating renewable energy resources into the energy Internet, the smart load integrated with the ES will play a greater role in the optimal operation of the distribution network. Here, the power flow optimal model of distribution network with the ES is proposed. Under different load levels, the flexible regulation of ES can reduce the overall voltage drop and optimise the operation of distribution network. The benefits of ES for the optimisation of distribution network are verified based on an improved IEEE 33‐node case. Numerical results show that the ES relieves the voltage drop of the distribution network and improves the reliability of distribution network based on the interaction between the ES and NCL. The overall energy efficiency and reliability of the distribution network system are improved.