The invention discloses a method and device used for power load aggregation. The method and device used for power load aggregation comprise S1, acquiring sample data of n transformer substation comprehensive load static characteristics; S2, mapping the sample data to a Hilbert space through a gaussian kernel function and acquiring samples; S3, confirming an initial aggregation center by selecting K samples in the samples; S4, performing aggregation calculation on mapped samples in a core space by adopting a k-means algorithm, and assigning each sample to closest-type upper and lower approximations according to an upper and lower approximation method; S5, dynamically adjusting weights omega1, omegabnr according to a current iteration; S6, calculating a Jomega value according to an arithmetic convergence criteria, and judging whether |Jomega(t)- Jomega(t-1)|<= epsilon or t>=tmax, if yes, then generating a final collection and finishing, if not, then entering into S7; and S7, enabling t=t+1, reconfirming an aggregation center and transferring to S4. The method and device used for power load aggregation is simple, easy, fast and effective, aggregation results are reasonable, and has important significance on practicability of load modeling research.