The utility model discloses a complex circuit board reinforcing plate applying tool which belongs to the field of flexible circuit board processing equipment. The tool comprises a pre-attaching machine upper heating plate, a pre-attaching machine lower heating plate and pins. A general-purpose tool pin sleeving plate, a general-purpose tool pin-removing plate and a steel sheet are sequentially arranged between the pre-attaching machine upper heating plate and the pre-attaching machine lower heating plate from the bottom up. Sleeve pin holes are uniformly distributed on the pre-attaching machine upper heating plate, the general-purpose tool pin-removing plate and the general-purpose tool pin sleeving plate. The sleeve pin holes on the pre-attaching machine upper heating plate, the general-purpose tool pin-removing plate and the general-purpose tool pin sleeving plate coincide. Applying clamp grooves are uniformly arranged on the steel sheet. The applying clamp grooves are rectangular grooves. The tool has the characteristics of reasonable structural design, flexible use, convenient operation and high working efficiency. The tool can satisfy demands of fixing circuit boards of different models.