For　traditional　dual-plane　on-axis　digital　holography,　the　robustness　is　lower　because　it　is　difficult　to　maintain　the　stability　of　the　phase　difference　between　the　object　beam　and　the　reference　beam,　and　it　may　be　invalid　when　the　objects　are　on　the　surface　of　a　medium　with　uneven　thickness.　An　improved　dual-plane　digital　holographic　method　based　on　Mach-Zehnder　interferometer　is　presented　to　address　these　problems.　Two　holograms　are　recorded　at　two　different　planes　separated　by　a　small　distance.　Then,　the　zero-order　image　and　conjugated　image　are　eliminated　by　Fourier　domain　processing.　In　order　to　enhance　the　robustness　of　the　system,　the　object　is　illuminated　by　a　stochastic　beam　that　is　a　speckle　wave　produced　by　a　diffuser.　Simulated　and　experimental　results　are　shown　to　demonstrate　that　the　proposed　method　has　greater　robustness　than　the　traditional　dual-plane　on-axis　digital　holography　and　it　can　be　used　to　imaging　on　the　irregular　surface　of　a　transparent　medium.