A homemade gas-flushing device of MAP has been introduced in detail. The device has made various needed gas mixture by measuring flow. All the components of the device can be bought in the market. Without any mechanical processing all the components can be directly used to making the device. The precision of this device was ±2%. The device was suitable for the test of meat packaging and edible fungi packaging, but not suitable for the test of fruit and vegetable packaging, for the limit of the measurement range of the float meters.