We　report　an　efficient　mechanism　to　generate　mechanical　entanglement　in　a　two-cascaded　cavity　optomechanical　system　with　optical　parametric　amplifiers　(OPAs)　inside　the　two　coupled　cavities.　We　use　the　especially　tuned　OPAs　to　squeeze　the　hybrid　mode　composed　of　two　mechanical　modes,　leading　to　strong　macroscopic　entanglement　between　the　two　movable　mirrors.　The　squeezing　parameter　as　well　as　the　effective　mechanical　damping　are　both　modulated　by　the　OPA　gains.　The　optimal　degree　of　mechanical　entanglement　therefore　depends　on　the　balanced　process　between　coherent　hybrid　mode　squeezing　and　dissipation　engineering.　The　mechanical　entanglement　is　robust　to　strong　cavity　decay,　going　beyond　simply　resolved　sideband　regime,　and　is　resistant　to　reasonable　high　thermal　noise.　The　scheme　provides　an　alternative　way　for　generating　strong　macroscopic　entanglement　in　cascaded　optomechanical　systems.　(C)　2020　Optical　Society　of　America　under　the　terms　of　the　OSA　Open　Access　Publishing　Agreement