Novel phase unwrapping algorithm for digital speckle pattern interferometry (DSPI) is proposed, which is mainly for the complex and discontinuous structure under the illumination of laser, the discontinuous area of phase is detected and identified through the subtraction of two speckle pattern interferograms,with opposite optical phases. Then improved unwrapping process based on the traditional line scan method is conducted in the region where phase is available, and the phase unrapping in the whole available area came out accurately and promptly. This algorithm is more efficient and simpler compared with others reported in the literature, and it can avoid the large phase discontinuous area effectively and conveniently. This novel phase unwrapping algorithm makes quantitative analysis in the actual engineering, such as distortion and vibration using DSPI very convenient.