The present invention relates to a method for generating a charge ID in Internet ONLY service, generating the charge ID that includes printable characters using a call ID in the IP gateway; the process is simple and resulted charge ID is absolutely unique. Wherein including: configuring the charge ID including 32 printable characters, each of which is represented with 4 binary bits; taking the call ID including 16 characters, each of which is represented with 8 binary bits; corresponding each call ID character with two charge ID characters, wherein the upper four from eight bits of one of the call ID characters referring to 4 binary bits of one of the charge ID characters, the lower four bits corresponding to 4 binary bits of another charge ID character. Because the scope represented by four binary bits is from 0 to 15, the charge ID characters can exactly correspond one by one relationship with printable characters of 0-9 and A-F.