The invention discloses a thick copper foil fine line fine pitch circuit board outer line processing method, which comprises a first step of preparing a PCB substrate; a second step of drilling PCB external auxiliary holes; a third step of carrying out first outer layer pattern transfer, including pasting a dry film on the PCB substrate and opening a window for all patterns according to the needs of customers; the fourth step of performing electro-coppering for all the patterns; the fifth step of removing the film, including taking the PCB substrate out of electroplating liquid and cleaning the dry film; the sixth step of drilling all PCB internal holes by taking the external auxiliary holes as the reference; and the seventh step of processing according to the normal flow. The invention uses thin-base copper plate material and performs the pattern plating for twice; the problem that the traditional use of a thick-base copper for the outer line is not conducive to fine line fine pitch preparation is avoided while the customer requirement for thick copper on an outer line is satisfied; and meanwhile, the pattern preparation difficulty is reduced and the product quality is improved.