A fastening system for a panel, comprising: at least two mounting rails, each having a plurality of engaging open cavities formed therein; and a plurality of engaging slide blocks, respectively engaging with the engaging open cavities, wherein the engaging slide blocks are adapted to fixedly connect a panel being disposed on the mounting rails; wherein the number of the engaging slide blocks is two and the number of the engaging open cavities is two, and the engaging open cavities respectively are a first engaging open cavity formed in a top surface of the mounting rail and a second engaging open cavity formed in a side surface of the mounting rail, characterized by a middle clamp, including a top flange which has two side lips respectively formed on two ends thereof adapted to engage with top frame strips of the panel for position limitation; a pair of vertical flanges being under the top flange and a flange support disposed horizontally between the vertical flanges, wherein the middle clamp is fixedly connected with one of the engaging slide blocks, which engages with the first engaging open cavity, via a fastening bolt; and an L-shaped fastener, including a vertical flange and a horizontal flange, wherein the vertical flange is fixedly connected with the other engaging slide block, which engages with the second engaging open cavity, via a fastening bolt, wherein a sliding open groove with a plane bottom is formed in one side of the mounting rail which is on the back side of the second engaging open cavity; and a back clamp, including a horizontal flange and a vertical flange, a side lip formed on each of the free ends of the horizontal flange and the vertical flange; and a bolt, having an end shape corresponding to the shape of the sliding open groove with a plane bottom and slidably disposed in the sliding open groove with a plane bottom, wherein the vertical flange and the bolt are fastened and the horizontal flange is adapted to fixedly connect with a back frame of the panel via a bolt. at least two mounting rails, each having a plurality of engaging open cavities formed therein; and a plurality of engaging slide blocks, respectively engaging with the engaging open cavities, wherein the engaging slide blocks are adapted to fixedly connect a panel being disposed on the mounting rails; wherein the number of the engaging slide blocks is two and the number of the engaging open cavities is two, and the engaging open cavities respectively are a first engaging open cavity formed in a top surface of the mounting rail and a second engaging open cavity formed in a side surface of the mounting rail, characterized by a middle clamp, including a top flange which has two side lips respectively formed on two ends thereof adapted to engage with top frame strips of the panel for position limitation; a pair of vertical flanges being under the top flange and a flange support disposed horizontally between the vertical flanges, wherein the middle clamp is fixedly connected with one of the engaging slide blocks, which engages with the first engaging open cavity, via a fastening bolt; and an L-shaped fastener, including a vertical flange and a horizontal flange, wherein the vertical flange is fixedly connected with the other engaging slide block, which engages with the second engaging open cavity, via a fastening bolt, wherein a sliding open groove with a plane bottom is formed in one side of the mounting rail which is on the back side of the second engaging open cavity; and a back clamp, including a horizontal flange and a vertical flange, a side lip formed on each of the free ends of the horizontal flange and the vertical flange; and a bolt, having an end shape corresponding to the shape of the sliding open groove with a plane bottom and slidably disposed in the sliding open groove with a plane bottom, wherein the vertical flange and the bolt are fastened and the horizontal flange is adapted to fixedly connect with a back frame of the panel via a bolt.