Abstract: A variable-rate spraying equipment was designed based on the GPS orientating technology and radar velocity measuring technology, and its control system software was developed. During the experiment, the spray dynamic capability was described by monitoring the spray parameters. This way can be used to measure the response capability of the equipment and can provide a reliable basis for the matching precision between spraying prescription and equipment. The experimental results showed that the spray uniformity was affected by the response lag when the flow error at constant application rates could be controlled within 4.65%. Selecting the proper speed and setting aside some time in advance could reduce the effect to a certain degree.