The method of extrapolation introduced by Cuilli-Cutkosky-Deo is applied to estimate the PYK coupling constant from the K±-p forward scattering ampliutude. We use the low-energy K--p data combined with the data used in the analysis by Chao and Pietarinen. The result is gΛ2+0.8gΣ2=27±1, which is much larger than their result and hence indicates how important the low-energy K--p data in the analysis are. Since Martin and Perrin presented K--p data which contradict Dumbrais, Dumbrais and Queen’s compilation used in the present analysis, we also estimate the coupling constant corresponding to this choice of the data and obtain gΛ2+0.8gΣ2=11+5-2. However, if we discard all the K--p data in the momentum range from 0.3 to 2 GeV/c, the predicted coupling constant and real part strongly support the former choice.