A method which stabilizes the frequency of the slave laser in long time by confocal F-P cavity and stabilized He-Ne laser is reported. A frequency-stabilized He-Ne laser is employed as a reference, He-Ne laser and slave laser are injected to confocal F-P cavity which is scanned by a signal generator and a high-voltage amplifier at the same time. The transmission peak signals which are detected by photodetectors are delivered to data acquisition card. A program using LabVIEW software can determine all peak positions and calculate the relative position of transmission peak signals of He-Ne laser and the slave laser. Feedback voltage is generated to make the relative position of He-Ne laser and the slave laser equal to setting values, then the stability of He-Ne laser is translated to the slave laser. Using this method, a laser diode (DL 100) is stabilized at wavenumber of 11716.1706 cm-1and the frequency drift is less than ±2 MHz in one hour.