The utility model discloses a mounting assembly of a cam shaft. The mounting assembly comprises the cam shaft (1) with a plurality of shaft necks (2) and a mounting sleeve (3); the mounting sleeve (3) is connected with one end of the cam shaft (1); the diameter of the mounting sleeve (3) is less than or equal to that of each shaft neck (2); the length of the mounting sleeve (3) is more than the distance between the adjacent shaft necks (2). The mounting assembly can fast and conveniently mount the cam shaft into a shaft sleeve, the mounting accuracy and the work efficiency are improved, and the cam shaft is also prevented from being damaged.