This paper studies the problem of surveillance area of WVSN (wireless video sensor network) with obstacles, which is finding the optimized view-orientations for all video sensors to maximize multimedia coverage. In this paper, the characteristics of direction adjustable sensing model are discussed and the relation between sensors and obstacles is analyzed. Then, a coverage enhancement algorithm PFOFSA (potential field based occlusion-free surveillance algorithm) is proposed, which could effectively minimize the negative effect of occlusion and overlapping in the sensing field. In PFOFSA, three kinds of virtual centroid point are defined for simplifying the structure of effective region, occlusion region and overlapping region. Two kinds of relationship between virtual force and orientation rotation are constructed and made comparison in experiments. Finally, a set of simulation results are performed to demonstrate the effectiveness of PFOFSA. According to the experiments, PFOFSA could maximize the coverage of WVSN with obstacles and make higher coverage rate than other algorithms.