The invention discloses a synchronous phasor measuring device. The device comprises starting equipment, energy taking equipment and synchronous phasor measuring equipment, wherein the starting equipment is used to adopt an energy storage power supply to provide a starting current for the synchronous phasor measuring equipment, and switch a working magnetic core of the energy taking equipment according to current amplitude information detected by the synchronous phasor measuring equipment; the energy taking equipment is used to take energy from a power transmission line by using the working magnetic core, and output a corresponding current to supply power for the energy storage power supply and/or the synchronous phasor measuring equipment; and the synchronous phasor measuring equipment isused for carrying out synchronous phasor measurement on the power transmission line. The starting equipment switches the working magnetic core of the energy taking equipment according to the current amplitude information so that the working magnetic core in the energy taking equipment can use a current mutual inductance principle to carry out energy taking and power supplying, and the reliabilityand safety of the energy taking equipment are increased. Extra measuring equipment does not need to be arranged, and a size and cost of the synchronous phasor measuring device are reduced under the condition that a device measuring function is ensured to be reliably realized.