Since Amir planted the watch and money in Hassan's room, it was obviously his intent for Hassan to be blamed for the theft. Amir's jealousy over his father's close relationship and patronage with Hassan caused him to make this unfortunate decision. When Amir announced that the money and watch were missing, he expected Hassan to be blamed. What he did not expect was for Hassan to accept the blame and for Baba to forgive him for the theft. Nevertheless, the shame of the affair was too much for Ali, and he decided to move out of Baba's home.
In the book The Kite Runner,Amir has always had a deep rooted sense of jealousy over Hassan's ability to stand up for himself and others which Amir did not have. His father, Baba, looked down on Amir because he did not possess this quality. In addition, Hassan had also taken up and protected Amir.
When Hassan is cornered by Assef and his friends and is raped by Assef. Amir is witness to the incident but hides. He does not have the courage to stand up and to try and protect Hassan. He can not even bring himself to face Hassan and projects his self hatred and shame onto Hassan. Everytime he sees Hassan it reminds him of his own shame.
In order to get rid of having to see Hassan and to keep being reminded of the shame, Amir sets Hassan up by planting the items in his bed in order to have him sent away.