The invention discloses an underdrain structure modified through a concrete pavement and a construction method of the underdrain structure. A plurality of water collecting wells are arranged on one side of the concrete pavement at equal intervals, and multiple trenches which are in one-to-one correspondence to the water collecting wells are formed in the concrete pavement at intervals in the length direction of the concrete pavement; the trenches are each shaped like a long strip, and the trenches are arranged in the width direction of the concrete pavement; and one end of each trench communicates with the corresponding water collecting well, and a water permeable surface layer and a water permeable layer are laid in each trench from top to bottom. According to the underdrain structure modified through the concrete pavement and the construction method of the underdrain structure, large-area concrete pavement breaking is avoided, and installation of too many drainage and seepage pipes is avoided.