For the manufacturing system adjusted, there still is the uncertainty in the manufacturing process which is part of poor information problem with probability distribution unknown. The statistical evaluation methods depend on information with known probability distribution, which can not used to realize to evaluate the stability of the manufacturing process. Hence it is urgent to solve the problem above. Firstly, the output experimental data in the manufacturing process are selected to establish the membership function according to the fuzzy norm method. Under the given confidence level, the measurement uncertainty of the experimental data can be estimated to characterize the uncertainty of the manufacturing process. Then the relative error of the measurement uncertainty can be obtained, which can evaluate the stability of the manufacturing process. Therefore, based on the fuzzy set theory, an evaluation method for the stability of the manufacturing process using the fuzzy norm method is proposed to make up for the deficiency of the statistical methods.