The present invention relates to a method of computer based data card software downloading and updating, in which, the data card connects with computer via data communication interface and acts the power on initial process at same time, the data card downloads software kit from computer to RAM memory, and the data card operates the software kit downloaded to the RAM memory. With this method of computer based data card software downloading and updating, no any more expensive Flash memory to be used in the data card, a lower cost is thus resulted, the data card failure resulted from Flash memory damage could be avoided and hence the data card reliability is increased; In course of data card downloading the update program and software from computer, it just needs re-update again only even though in fault, the complete operation is convenient and rapid with a wide suitable field, this lays the foundation of the advancing and development for the data communication peripheral equipment technology of portable equipment.