A mounting assembly (1) for a solar panel, comprising beams (10), pressing blocks (30) and a plurality of anti-slip blocks (40), said beams (10) are paralleled and transversely fixed to installation part outdoors, and the upper portion of said beam (10) is provided with a long groove (101) along the longitudinal direction of the beam, and the opposing side walls of said long groove (101) extended to said groove (101) to form a supporting portion (102), one end of said anti-slip block (30) is slidably inserted into said long groove (101), the other end of said anti-slip block (30) is loaded on said supporting portion (102) and is fixed to the back of said solar panel, and said pressing block (20) is pushed and pressed on the side edge of said solar panel and is fixed to said beam (10). The installation of solar panel can be realized by inserting the anti-slip block (30) in the back of solar panel into the long groove (101) of beam (10), the operation is easy and can bring amazing stability; furthermore, spare of the setting of strengthened rib with great span disposed on the solar panel, only if the use of beam (10) and anti-slip block (40) with small volume, further simplifying the mounting structure and saving material, so as to reduce the cost of human source and material. Besides, a method for assembling solar panel is disclosed in the present invention.