Van Genuchten model is one of the most commonly and widely used models. Existing research results show that different forms of parameter m and whether the correction factor is taken into consideration can have a great impact on the fitted parameters of Van Genuchten model. Therefore

three forms of parameter m (m refers to (a) without constraints; (b) ; (c)

respectively)

as well as correction factor were studied in the paper. MATLAB was used throughout the calculation process. The effect of Residual matrix suction and on fitted parameters (i.e.

parameters of a

m and n) were discussed based on sixty-seven types of SWCC data. The results show that if m is not constrained

a and n decrease and m increases with increase of . If m is constrained

a decreases and n increases with increase of . Furthermore

the discrete degrees of a and n increase and discrete degree of m decreases when applying the correction factor given a non-constrained m

while discrete degree of a increases and discrete degree of n decreases when m is constrained. The results also indicate that the parameter a under various conditions of m and shows a linear correlation of parameter a without any constraints

while for parameter n

the rule does not exist.