The paper proposes an immune mechanism based path planning algorithm of deterministic mobile robot for the contradiction between the certainty of mobile robot path planning and the search space of the algorithm. Firstly, for ensuring the positive solution space fully covered by the initial point of the path and the secondary node, an initial antibody population is constructed using the vaccine heuristic rule in the positive environment space, which is determined by the perpendicular line of the initial point and the target point of the path. Then, antibody cloning is carried out according to the number of positive tangent points, and the subsequent node is reconstructed and mutated under the inspiration of vaccine. In addition, the improvement rate of single-point antibody reconstruction is presented to dynamically adjust the number of antibodies and expand the search space of antibodies. To realize the deterministic path search, the algorithm uses the number of antibody nodes to judge the mutation times of antibody and decided the evolution times of antibody population. Finally, the proposed algorithm is compared with other algorithms in different working condition. The results verify the certainty and effectiveness of the proposed algorithm, and the optimal solution is balanced between the path distance and the steering cost, which is more in line with the motion requirements of the mobile robot.