The invention relates to the technical field of nondestructive testing and evaluation of insulating materials, specifically to a manufacturing method and a pressing die for a standard micro-crack defect test block. The manufacturing method comprises the following steps: selecting an insert with a thickness identical to the width of a micro-crack defect required to manufacture, fixing the insert on an inner insert and successively putting a lower pressing block, the inner insert, a test block powder and an upper pressing block in the die so as to accomplish assembling of the pressing die; and then carrying out test block pressing and subjecting the test block to demolding and sintering after completion of pressing. According to the invention, the thickness of the insert is identical to the width of the micro-crack defect required to manufacture, the insert is fixed on the inner insert, then the pressing die is assembled, and test block pressing, demolding and sintering are successively carried out; so the obtained test block can calibrate detection sensitivity of X-ray real-time imaging detection technology and ultrasonic detection technology.