Abstract: The two-sided stochastic assembly line balancing problem of Type I (TSALBP-I) with the uncertainty of task times considered is discussed in this paper. It is assumed that the task times are distributed according to normal distribution. Based on this assumption, a mathematical model is presented for the problem and then a heuristic algorithm is proposed. By this algorithm, in selecting and assigning tasks to workstations, it sets a higher priority to the task that has operation position constraint. Different solutions can be obtained by changing the pre-determined limit probability under different cycle time. The effectiveness of the proposed algorithm is demonstrated by numerical results for a set of benchmark problems.