We present a new approach to the study of charge properties of dust particles in a dusty plasma. We adopt for the first time the detailed balance method developed earlier in the solid state physics. The present theory takes adequately into account the discreteness of the charge variations on a dust grain and operates in terms of probabilities to find one or other charge on a dust particle. The proposed equations, being solved analytically, give simple analytical expressions for the shape of the charge probabilities. We demonstrate that the charge distribution of a dust grain has a Gaussian form and the peak position is coincident with the charge derived in widely used Orbital Motion Limited (OML) theory. It is shown that the relative charge fluctuation on a dusty grain is increased with decreasing the dust size. The proposed method also enables us to obtain sone useful information concerning statistical and thermodynamic properties of dust grains in the space dusty plasma. We present simple analytic expressions for statistical and thermodynamic properties of dust grains in the space dusty plasma and discuss the results of our theoretical approach in terms of statistical theory and plasma physics.