The invention provides a device and method for installing and positioning pillars for outdoor switchgears of a thermal power plant. The device is formed by combination of two symmetrical components, wherein each component comprises a horizontal semicircular ring disc, a semicircular pipe tile, directional wings, a handle and magnet ring bars; the semicircular ring disc is a semi circular ring; each directional wing is in a rectangle shape after being cutting off an isosceles right triangle from a corner; the semicircular pipe tile is a semicircular cylindrical surface; the magnet ring bars are inlaid on the side of the semicircular pipe tile; one end of the semicircular pipe tile is connected with the semicircular ring disc; the long side of each directional wing is connected with the outer wall of the semicircular pipe tile; the short side of each directional wing is connected with the semicircular ring disc; the two adjacent directional wings are vertical to each other; the handle is connected with the outer wall of the semicircular pipe tile; and the magnet ring bars combine the two components as a whole. The method is characterized by installing the device in the correspondingposition of a pillar, adjusting the directional wings, ensuring the cross line of a support steel plate to be identical with the directional wings, adjusting the pillar, ensuring the directional wings of the device to coincide with the cross line in the center of a foundation cup rabbet and fixing the pillar stably with precast concrete wedges, wherein the deviation of the center line of the pillar is not more than 2mm; and the verticality deviation is not more than 3mm.