To the teacher in charge of student affairs:

Hello, I am XXX, a sophomore majoring in XXX at X University. I am writing this letter to apply for joining the student union.

As an active university student, I have been actively participating in various activities since my freshman year. During this period, I have accumulated rich experience and honed my organizational skills. At the same time, I also understand that there are many problems that need to be solved in our university's current student union work. Therefore, if given the opportunity to join the student union, I will use my own strengths and enthusiasm to contribute my own strength to promote the development of our school's student union work.

I believe that with my enthusiasm for serving students and dedication to selfless dedication, as well as organizational ability and communication skills acquired through various activities over the past two years, I can make a positive contribution to our school's student union work if given an opportunity.

I look forward to your kind consideration of my application! Thank you very much!

                                                           Sincerely yours， 

                                                     XXX