The more coal production is produced, the more waste is coming from the combustion process which leads to the environmental pollution. Waste from burning coal in the form of fly ash can be used as a mixture of subgrade stability in highway construction. The purpose of this study is to determine the characteristic value of each combination of fly ash, Liang Anggang sand and cement as a mixture of subgrade layer materials. The test objects consist of 10 combinations of fly ash, Liang Anggang sand and cement. Some tests were conducted such as Atterberg Limits, Specific Gravity, Sieve Analysis, Compaction and CBR test, respectively. From all combinations of the test objects, the best combination that suits the characteristic values of a subgrade layer mixture is a combination of minimum 6% of CBR specification and a maximum of 6% of Plasticity Index (PI). The recommended economical combination for landfill soil is a combination of test objects with a composition of 75% fly ash, 20% Liang Anggang sand and 5% cements.