Post-tensioned unbonded prestressed tendons conforming to parabolic shapes are widely used in prestressed concrete slabs. Due to construction deviations, even if numerous supporting reinforcements are introduced along the tendon at intervals to control the vertical positions, the final shape of the curve may differ significantly from a real parabola. This paper proposes a catenary-cantilever curve shape, allowing unbonded prestressed tendons to be located by controlling only the top and bottom points, instead of numerous shape-governing points. By solving the curve equations, we undertake a comparative analysis between the shape features of the catenary-cantilever curve and parabola curve. Subsequently, the friction loss of the prestressed tendons are obtained. The results show that for common slab spans, although some geometrical characteristics of the catenary-cantilever curve, e. g., the position of the inflection point and the height ratio of the curve, differ significantly from those of a parabola, the friction loss discrepancy of the two shapes is not considerable and can be neglected in the total prestress loss. The deflection analysis conducted using ANSYS reveals a striking resemblance in the inverted arch deflections of the two shapes, implying that the balance load effects of the prestressed tendons with the two shapes are close.