On the Approximation Properties of Ces\`{a}ro Means of Negative Order of double Vilenkin-Fourier Series

In this paper we establish approximation properties of Ces\`{a}ro $% (C,-\alpha ,-\beta )$ means with $\alpha ,\beta $ $\epsilon $ $(0,1)$ of Vilenkin-Fourier series.This result allows one to obtain a condition which is sufficient for the convergence of the means $\sigma _{n,m}^{-\alpha ,-\beta }(x,y,f)$ to $f(x,y)$ in the $L^{p}-$metric.