A manual slope-adjusting mechanism for an elliptical cross trainer having a front sleeve with side tubes at both sides of the bottom of the front end of the elliptical cross trainer. An upright tube is positioned at the center of the front sleeve. A toothed portion is formed at the top of the upright tube. Moreover, a control lever is attached to a coupling rod disposed within an upright support of the elliptical cross trainer. The other end of the coupling rod enables an up-and-down movement of a locking element such that the locking element can be engaged into or disengaged from the toothed portion of the upright tube. In this way, the supporting angle of the side tubes can be manually adjusted for adjusting the slope of the plank connecting rods.
