Guide mechanism enabling installation to be in place once

The invention discloses a guide mechanism enabling installation to be in place once. The guide mechanism comprises a connecting mechanism for separating a connecting bolt from a block nut. The bolt is installed on the upper portion of the connecting mechanism in a movable manner in a vertical direction. The block nut is installed on the lower portion of the connecting mechanism in a rotary manner in a vertical direction. The thickness of the block nut is smaller than the width of the upper surface of the block nut. When a solar cell panel needs to be fixed, the width of a through groove in the upper wall of a T-shaped groove of a fixing support should be smaller than the thickness of the block nut, and during installation, the block nut is rotated till the block nut can pass through the T-shaped through groove, and then the block nut is directly put into the T-shaped groove from above. In this way, installation is quite convenient.