Randomicity of basic variable results in the problem of structural reliability. A series of statistical parameters is applied in reliability calculation. Statistical parameters are attained by the statistics and analysis of source data of basic variable. However the basic variable source data is imperfect for a lot of structure. On the other hand, the relation of reliability index and basic variable is an important issue in reliability calculation. The two matters are solved in this paper by fuzzy mathematics. First, the matter of statistic data scarcity of load and resistibility and offered scientific evidence for estimation of distributing type of load and resistibility it solved by grey forecast; Second , the correlate degree of reliability index and load is calculated by correlate degree theory which can provide scientific evidence for security inspect of project.