This paper presented a novel particle filter called Inner-Contour Particle Filter to track unclosed contour under complex background. Aimed at achieving effectiveness and robustness against complex background, the proposed algorithm first used Canny edge detector to detect the edge information along the normal line of the contour, and then sampled the inner part of the normal line to get the local color information and combined it with the edge information to construct a new normal line likehood. After that, all the inner color information was used to construct a global color histogram. Finally, the edge information, local color information and global color information were integrated to form a new conservation likehood. Experimental results show that the proposed method is robust and computationally efficient for tracking contours under complex background, and can run in realtime completely.