To solve the problem of Energy Management Unit (EMU) of electric vehicles, we develop an automatic test system. MCU of Frescale MC9S12 series is used as master chip. Upper computer, lower computer and unit to be tested are connected with CAN. 6 different tests of unit and its 4 types of PCBA can be tested by automatic test system. The test items can be configured highly flexible. Upper computer software shows the test results in real time, saves the data to the database and creates the Word table. After the early testing, all tests of one kind of PCBA can be finished in 1 minute. The absolute error of the automatic test system is less than 0. 05V,? and its fault detection rate is 100%.