The electronic devices need to pass the electromagnetic interference test, to validate it can work safety in the electromagnetic interference environment. In the traditional test, the position fixation of the tested device is clamped the device by hand, which reduce the test efficiency and harm to operator’s health. Here, we designed an automatic grasp equipment and proposed an adaptive-fuzzy-based control method for grasping stability. This device is driven by two pneumatic slide rails to realize the synchronous motion control in the x and y-axis directions. A gas flow sensor is installed in the inlet pipe to estimate the amount of air entering the pneumatic cylinder. A force sensor is installed on the contact surface between the grasper and the object. Adaptive-fuzzy-based control algorithm applied in grasping the object with different sizes quickly and stably. The experimental results show that the stable grasping force is 10% by weight, the grasp time is 0.3s from contacting to the stable grasping state. The grasping force can be sustained and stable even external disturbing forces are applied to the tested object. Our control method has great potential of applying in the automatic testing equipment.