A testing circuit board used in a testing system with a tester and a handler is disclosed. The testing circuit board is used for transmitting a plurality of testing signals provided by the tester to test at least two devices under test located on the handler. The testing circuit board includes a connecting board, a load board and at least two connecting interfaces. The connecting board coupled to the handler has at least two connecting sockets for respectively connecting to the devices under testing. The load board coupled to the tester has two joining sockets located corresponding to the connecting sockets. The at least two connecting interfaces are coupled between the connecting sockets and the joining sockets for transmitting the testing signals for testing the devices under testing.