The invention discloses biologically related substances modified by a multifunctional H-type polyethylene glycol derivative. The derivative comprises a linear main axis LPEG and four PEG branched chains, and n1, n2, n3 and n4 are polymerization degrees of the branched chains, respectively; U1 and U2 are trivalent branching groups connecting the main axis LPEG with two PEG branched chains; F1 and F2 contain functional groups or their protected forms R01, and the number of R01 is one or more than one. Any linking group in the molecule or linking groups formed with adjacent heteroatom groups are stable or degradable; any PEG chain segment in the molecule independently shows polydispersity or monodispersity. One H-type molecule can modify multiple types of or multiple biologically related substances; the modified product has a flexible branching structure, a high drug loading capacity, optimized pharmacokinetics and tissue distribution, and can also carry two biologically related substances with different functions, so as to generate fluorescence property or targeting function.