The external cavity laser diode array (LDA) with volume Bragg grating (VBG) recorded in photo-thermo-refractive (PTR) glass as wavelength selected element is studied experimentally. The influence of fast-axis-collimation on coupling efficiency is studied. Experimental results indicate that the wavelength of the LDA is locked and the line-width is narrowed sharply under the effect of VBG external cavity. The influence of VBG reflectivity on spectral characteristics and efficiency of external cavity LDA is studied mainly. Experimental results show that the increase of VBG reflectivity can inhibit the intra-cavity mode effective and enhance the contrast of spectrum and narrow the line-width. Using the VBG with a reflectivity of 30%, an output power of 24.8 W is obtained with the linewidth down to 0.18 nm, which corresponds to the efficiency of 82.6% compared with the output power in free-running LDA.