Pluronic copolymer L61 was found to possess a stealth function for liposomal drug delivery, comparing favorably to PEG. The liposomes modified with 0.1% L61 (w/w) were long-circulating, and preferentially accumulated in the tumor site. The paclitaxel-loaded L61-liposomes with a single injection dose could successfully arrest the tumor growth, lasting for five days, and displayed better treatment outcomes compared to the non-modified liposomes and even the PEGylated liposomes.