A reliability determination method, which is configured to test a batch of semiconductor devices, includes: obtaining a Welbull distribution of lifetime of the batch of semiconductor devices; dividing the Welbull distribution into at least a first section and a second section, wherein the first section and the second section meet a confidence interval; generating a first trend line of the first section and a second trend line of the second section according to the first confidence level, in which the first trend line has a first slope and the second trend line has a second slope; determining the first slope exceeds a second slope; and determining a predicted reliability of the batch of the semiconductor device under a target quality level according to the first section.