A kind of coded-source-imaging-based laser probing diagnostics can be used for the measurements of coronal region electron density in the explosion experiments of wire array Z - pinch. Based on the shadowgraphy system, it just add a linear fringe-pattern mask in front of the target to change the wavefront distribution of incident laser. The selection of object plane and extraction of deflection angle are analyzed by imaging simulation. When the maximum density of plasma is an order of magnitude less than the critical density, paraxial approximation can be used in Abel transform. Cubic spline interpolation of deflection angles and piecewise integral of Abel transform give out the density distribution, which is in good agreement with the setted density value. Compared the inversion errors with different line-pairs coded masks, we can get good results for the plasma with smooth gradient even if the mask fringes are relatively sparse. Calculation shows that this method has a simpler system, and don′t need high performance parameters for light source and optical device, thus it has a good measurement adaptability, and it′s feasible for the diagnosis of plasma density.