As a source searching method, infotaxis has been used in mobile olfactory robots equipped with contact-type MOS (metal oxide semiconductor) gas sensors. This method navigates a robot to explore more cues in the global space and therefore costs much time at the early stage. To solve this problem, this paper presents a line integral infotaxis (LII) algorithm which is realized by applying a remote-type TDLAS (tunable diode laser absorption spectroscopy) gas sensor to the infotaxis. In addition, the robot often gets stuck in the place of high concentration during the infotaxis searching process, so an odor source declaration procedure which is implemented by calculating the odor particle flux on a closed curve is added to the LII. Simulation results show that the LII algorithm can enormously save time of exploration and solve the local convergence problem.