The aim of this paper is to design and implement a low noise amplifier (LNA) based on transformer for a Ku-band application. The proposed CMOS LNA can have an enhanced gain because of the cascade topology, a highly flat gain response because of the RC feedback network, and a wide passband because of the source degeneration structure that effectively suppresses the Miller effect. The Ku-band LNA dissipates 22.175 mW power and achieves the S11 of -10.31 to -6.77 dB, S22 of -18.1 to -37.78 dB, flat S21 of 8.78 to 10.59 dB, and noise figure of 3.96 to 5.33 dB across the 12~18 GHz span. The measured output P1dB is approximately -2 dBm. The chip size including all testing pads is only 0.545 x 0.599 mm2.