A soft X-ray laser Mach-Zehnder interferometer was used to diagnose electron density Ne of spot-focused CH plasma on Shengguang II facility, and the experimental results were presented in this paper. Density reconstruction was performed by making Abel transform, 2D distribution of Ne was obtained, and the highest Ne was about 3.2×1021cm-3. Comparing with simulation results of JB19 code (1.5D) and XRL2D code (2D), it was found that the theoretical result with flux-limited factor of 0.05 agreed with reconstructed result in high density area, but experimental result gave an Ne distribution declining faster. Furthermore, 2D Ne distribution of simulation differed much from that of experiment in details. A brief error analysis showed that flatness error of interferometer dominated the experimental error.