Orthogonal　eigenmodes　in　multimode　waveguides　are　an　indispensable　physical　dimension　for　enhancing　the　capacity　of　optical　communications,　and　efficient　mode　converters　are　therefore　of　vital　functional　significance.　However,　the　conventional　single-pair　mode　conversion　in　a　single　device　is　having　difficulty　meeting　the　ever-increasing　demand　for　optical　capacity.　By　contrast,　the　multi-pair　mode　converter　can　improve　the　multiplexing　capacity　and　be　further　applied　in　spatial-mode-oriented　passive　signal　switching　and　permutation　cipher.　Here,　a　scalable　multi-mode　converting　model,　combing　the　multimode　interference　and　beam　shaping　by　exploiting　subwavelength　metamaterials,　is　firstly　reported　to　enable　simultaneous　multi-spatial-mode　manipulation　and　break　its　polarization-dependency　limit.　Based　on　this　model,　five　proof-of-concept　converters　are　designed,　realizing　polarization-independent,　and　multi-mode　conversions,　or　a　combination　of　both　within　compact　lengths　(<　17.436　mm).　For　the　first　time,　TE0/TM0-to-TE2/TM2,　TE0/TE1/TE2-to-TE2/TE3/　TE4,　TE0/TE1/TM0/TM1-to-TE2/TE3/TM2/TM3,　and　TE0/TE1-to-TE1/TE2　converters　are　reported　and　experimentally　demonstrated,　covering　a　double/triple/quadruple-mode　manipulation　in　a　single　device.　From　measurements,　these　converters　exhibit　low　insertion　losses　(0.72　to　1.65　dB)　and　intermodal　crosstalks　(-30.26　to　-12.19　dB)　at　1550　nm,　and　have　a　56-nm/30-nm　bandwidth　of　loss　<　1.4　dB/1.9　dB　and　crosstalk　<　-13　dB/-10.5　dB,　for　the　best/worst　case.　The　proposed　multi-mode　converting　model　can　manipulate　multiple　input　modes　in　parallel　and　beak　the　polarization-dependency　limit　for　multi-spatial-mode　conversion,　which　holds　great　potential　for　spatial-mode-oriented　nanophotonic　systems.　IEEE