Weighted stego-image (WS) method is famous for estimating embedding rate of steganography using least significant bit (LSB) scheme. This paper investigates its feasibility of analyzing pixel-value differencing (PVD) steganography, an algorithm without using LSB strategy. Theoretical analysis demonstrates that, although PVD embedding scheme is quite different from LSB, the stego noise in sum value image behaviors like that of LSB replacement (LSBR) steganography. Thus, several sum value image based WS estimators are proposed and the effectiveness is verified via experiments. The results indicate that the estimators are sensitive to sample size and relative embedding rate, and combing non-adaptive and adaptive methods can make the estimation more accurate.