A third order Gm-C reconfigurable Butterworth low-pass filter for SDR receivers with a tunable cutoff frequency of 5M to 50M is presented. A positive feed-forward compensation Gm-cell is utilized to improve the linearity of the filter. The filter has been implemented in SMIC 130nm CMOS process. It occupies 0.63 〖mm〗^2 die area and consumers 12mA - 16mA current with a 1.2V power supply. The measured in-band IIP3 is about 10.5dBm, and out-band IIP3 up to 26.3dBm.