Main cause of early cracking within mass-concrete structures is thermal stress owing to cement hydration. Comparing resulted thermal stress with tensile strength of concrete must be necessary to avoid thermal cracking. In most cases, the analysis uses F.E.M., whichis not economical. In order to clear away the economical problem, simple system of thermal stress analysis is constructed with personal computer here. The system shows good applicability to simple shaped structure to be able to approximate one dimensionally.