In this study, a practical and straightforward method is presented for measuring the optical feedback coefficient C and the linewidth enhancement factor α by means of the mode-hopping phenomena in the self-mixing interferometric system. A theoretical analytical model, in combination with the laser energy transition area of the phase jumping points and the C-parameter, is described deeply. In the experiment, a laser self-mixing vibration sensing system is fabricated to further verify this proposed theoretical model and simultaneously obtain the geometric area SR,F under different C values. From the actual measurements, the C-parameter is exactly measured by tracking the change of the geometric area SR,F, over the range of 1.0-4.5. Then, the α-factor of this self-mixing sensor is obtained as 2.41±0.15 with an accuracy of 6%. In addition, the absolute and relative error of the experimental results are less than 0.14 and 7.43%, respectively. In a word, the measured results agree well with the simulated values, of which validates the good applicability and practicability of this measurement method.