In this paper, an active-integrated leaky-wave antenna with power combining scanning capability is presented. This leaky-wave antenna with the novel perpendicular L-shape topology is integrated with a varactor-tuned high-electron mobility transistor (HEMT) voltage controlled oscillator (VCO) on the same plane. Changing the VCO frequency, we can control not only the dual-beam scanning angle but also derive the power combining effect with the sum (L) or difference (A) radiation patterns. The power combing effect of difference mode, which is the dual-beam pattern and the sum mode pattern, which is a 3-beam pattern, with the 3rd beam located along the middle direction (450, 1350) of the X and Y axes. The measured scanning angle is steered over a range of 24-460 for the right beam and 127-1480 for the left beam. Compared with single microstrip leaky-wave antenna, the L-shape LWAs configuration has the advantages of switchable radiation patterns as the VCO varied from 10GHz to 10.6GHz.