To counter the uncertainty of the processing time in the practical production process, this paper builds a single machine earliness/tarliness with fuzzy processing time. Optimum processing time is obtained and the minimum target function is got on the basis of taking penalty coefficients of the task, set-up time and value acquisition in the range of fuzzy processing time into consideration. The optimum processing sequence of the task is set by adopting the technique of simulated annealing and in the end in illustration of it a simulation case is put forward.