We　theoretically　investigate　the　stability　of　a　two　cascaded　cavity　optomechanical　system　with　optical　parametric　amplifiers　(OPAs)　inside　the　two　coupled　cavities,　and　study　the　steady-state　entanglement　between　two　distant　mechanical　resonators.　We　show　that　the　parameter　regime　where　the　system　is　unstable　without　OPAs,　such　as　relatively　high　laser　intensity　and　blue　detuning,　can　be　exploited　to　build　the　steady-state　mechanical　entanglement　by　modulating　the　parametric　gain.　The　application　of　OPAs　is　helpful　to　preserve　the　mechanical　entanglement　suffered　from　the　dissipation　at　some　finite　temperature.　The　scheme　provides　an　alternative　way　for　improving　and　engineering　the　quantum　entanglement　of　two　distant　mechanical　oscillators.