This paper presents a design for test the embedded flash in an object System-on-a-chip (SoC). The feature of the Flash TAP (Test Access Port) complies with the IEEE std.1149.1, and it can select different scan chains and other control registers for other test. By the trade-off between the test time and the circuit area, an IST (In System Test) circuit is designed in the SoC. Experiment results on the embedded memory have shown that the proposed method costs small testing timing by the use of IST.