The inject-locking on a magnetron is a key technique to achieve coherent power combining to extend the power capacitance of magnetrons. The improvement on the output spectrum of a 1 kW Continuous Wave(CW) magnetron at S-band is presented. The influence of the filament current on output characteristics of the magnetron is studied. The bandwidth of the free oscillating magnetron is reduced from 10 MHz to 300 kHz by decreasing its filament current. The inject-locking bandwidth of the CW magnetron has been expanded to 14 MHz by increasing the injection signal power. The External Quality Factor(QE) of the magnetron evaluated from the Adler equation varies from 52 to 72 at various injecting power ratios.