Influences of external optical feedback effects on characteristic of the fiber Bragg grating external cavity semiconductor laser are investigated. When the effect of temperature on the wavelength of external cavity semiconductor laser is taken into account, an external optical feedback setup is built, and the optical feedback intensity can be adjusted. The linewidth of the external cavity semiconductor laser is measured by delayed self-homodyne technique, and the changes of linewidth and noise of the laser with different external optical feedback are analyzed. Experimental results show that the linewidth of the laser decreases when the optical feedback intensity increases. The linewidth is narrowed down to 15% of the original one when the feedback ratio reaches -22 dB. Meanwhile, within the same variation of the optical feedback, the relative intensity noise of the laser has no obvious change until the feedback ratio increases to -27 dB. As the feedback further increases, the relative intensity noise of laser increases significantly and the coherent collapse happens inside of lasers.