Objective To compare the differences in dynamic stability and cost of dual-task stability during walking with different dual tasks. Methods Kinematics data of 40 subjects walking with different dual tasks were collected by three-dimensional (3D) motion capture system, and the related dynamic stability indexes were indirectly calculated. One-way repeated measures ANOVA was used to compare gait parameters and dynamic stability between single-task walking and different dual-task walking. Two-way repeated measures ANOVA was used to analyze the effects of dual-task types (cognitive tasks and motor tasks) and task loads (simple tasks and difficult tasks) on cost of human dual-task stability and the interaction between them. Results Compared with the single task, the pace under intervention of different dual tasks decreased (P<0.05), the pacing frequency and dynamic stability increased (P<0.05), the step length under intervention of double motor loads was smaller than that during single-task walking (P<0.05), and the step length under intervention of a single cognitive task and double cognitive tasks was larger than that during single-task walking (P<0.05). The stability cost of a simple cognitive task was higher than that of a simple motor task (P<0.05), the stability cost of a difficult cognitive task was lower than that of a difficult motor task (P<0.05), and the stability cost of a simple motor task was lower than that of a difficult motor task (P<0.05). Conclusions Compared with single-task walking, the intervention of different dual tasks will increase dynamic stability of human body. For the stability cost of dual tasks, there are interaction effects among different task types and different task loads. When the task load is high, the dual-task cost of the cognitive task is low. Namely, the negative interference amplitude of the cognitive task increases, which will damage dynamic posture control ability of the body. When the second task is the motor task, the negative interference amplitude on dynamic stability of human body increases under a low load, which reduces dynamic posture control ability.