A modular support assembly for a solar power system comprising: a plurality of base units each of which includes a base frame capable of floating on a water surface and including a first tube member extending in a first direction, and a second tube member extending in a second direction transverse to the first direction and connected to said first tube member, and a plurality of solar panel supports disposed on said base frame; and a plurality of connection units each of which interconnects said base frames of two adjacent ones of said base units, each of said connection units including a pair of sleeve members and a plurality of fasteners, each of said sleeve members having a tubular portion sleeved on one end of said second tube member of said base frame of one of said two adjacent ones of said base units, and a blind flange connected to one end of said tubular portion and closing said one end of said second tube member, wherein each of said tubular portion and said blind flange is made of a polymeric material, said blind flange having an annular peripheral portion and a plurality of annularly spaced-apart elongate holes formed in said annular peripheral portion, said annular peripheral portion projecting radially and outwardly from said one end of said tubular portion; wherein each of said connection units further has an annular metal reinforcement piece embedded in said annular peripheral portion, said elongate holes extending through said annular peripheral portion and said annular metal reinforcement piece; wherein said blind flanges of said sleeve members abut against each other, said elongate holes of said blind flanges are aligned with each other for passage of said fasteners, and said fasteners fasten together said blind flanges. a plurality of base units each of which includes a base frame capable of floating on a water surface and including a first tube member extending in a first direction, and a second tube member extending in a second direction transverse to the first direction and connected to said first tube member, and a plurality of solar panel supports disposed on said base frame; and a base frame capable of floating on a water surface and including a first tube member extending in a first direction, and a second tube member extending in a second direction transverse to the first direction and connected to said first tube member, and a plurality of solar panel supports disposed on said base frame; and a plurality of connection units each of which interconnects said base frames of two adjacent ones of said base units, each of said connection units including a pair of sleeve members and a plurality of fasteners, each of said sleeve members having a tubular portion sleeved on one end of said second tube member of said base frame of one of said two adjacent ones of said base units, and a blind flange connected to one end of said tubular portion and closing said one end of said second tube member, wherein each of said tubular portion and said blind flange is made of a polymeric material, said blind flange having an annular peripheral portion and a plurality of annularly spaced-apart elongate holes formed in said annular peripheral portion, said annular peripheral portion projecting radially and outwardly from said one end of said tubular portion; wherein each of said connection units further has an annular metal reinforcement piece embedded in said annular peripheral portion, said elongate holes extending through said annular peripheral portion and said annular metal reinforcement piece; wherein said blind flanges of said sleeve members abut against each other, said elongate holes of said blind flanges are aligned with each other for passage of said fasteners, and said fasteners fasten together said blind flanges.