The invention belongs to the field of self-assembled polymer materials and discloses a chemical crosslinked pH value responsive multi-arm polymer and a nano-porous capsule. The polymer comprises a side chain and a main chain; the main chain is a triblock copolymer with a structural formula being block 1-b-block 2-b-block 3, the block 1 is a pH responsive polymer chain, the block 2 is a polymer chain forming a multi-arm bonding structure, and the block 3 is a polymer chain forming a chemical crosslinked structure; the side chain is a hydrophilic polymer side chain and grafted to the block 2. By introduction of the chemical crosslinked chain to the multi-arm polymer, decomposition of encapsulated drugs can be avoided, changing of external temperature is avoided, and simplicity in operation and quantification are realized. By design and regulation of components of each copolymer, crosslinking degree can be controlled.