A circuit structure free from test effect is provided. The circuit structure includes a first test terminal and a second test terminal. A symmetric circuit unit is coupled between the first test terminal and the second test terminal. The symmetric circuit unit includes a plurality of transistors, wherein the transistors are symmetrically disposed to form a first part circuit and a second part circuit. A switch control unit alternatively connects the transistors of the first part circuit and the transistors of the second part circuit between the first test terminal and the second test terminal according to a control signal.