The results of Russian and international practice of the code error evaluation, which used in the nuclear facilities safety analysis, are presented in the paper. The approach to the code error evaluation, based on the taking into account of the code simulation model parameters uncertainties and the uncertainties of the measurement in the validation experiments, is suggested. The review of Russian and international uncertainty analysis methods, which related with the code simulation model parameters uncertainties and used in the framework of the nuclear facilities safety analysis, is presented. The description of the application of the uncertainty method, based on the Wilks formula, is given. The suggestions about the improvement of the Russian federal rules and regulation and the safety guides in the field of the requirements for the code calculation error evaluation in the framework of the nuclear facilities safety analysis are discussed in the Conclusion.