Abstract: To explore the standardization of the in vitro Nb2-11 cell proliferation bioassay for recombinant human growth hormone (rhGH), we first tested the biological activity of 2 batches of rhGH drug substances, 3 batches of rhGH for injection, and 24 batches of rhGH injections, based on which we proposed the experimental effective criteria. Furthermore, we conducted methodological validation in accordance with General Rule 9401 of the 2020 edition of the Pharmacopoeia of the People's Republic of China. Subsequently, the inter-laboratory consistency, intra-laboratory and inter-laboratory precision of seven labs were studied by determining the in vitro bioactivity of six batches of rhGH products and two batches of rhGH drug substances from four different manufacturers using this method. The consistency of the in vitro and in vivo bioassays was assessed by evaluating 28 batches of rhGH drug substances with both methods. Finally, multiple batches of rhGH samples with different expiration dates were tested to determine the standard limits of the bioassay. The results of this collaborative study indicate that the Nb2-11 cell bioassay exhibits good intra- and inter-laboratory reproducibility, with a 100% pass rate for the experimental effective criteria. The Nb2-11 cell bioassay had high consistency with in vivo animal bioassay. Animal experiments were approved by the Experimental Animal Welfare Ethics Committee of China National Institute of Food and Drug Control (approval number: NIFDC (Fu) No. 2024 (B) 004). This method is applicable to rhGH drug substances and products from different manufacturers. Collectively, the Nb2-11 cell bioassay can be used as a standardized method for determining the biological activity of rhGH products, replacing in vivo animal methods for quality control and release testing.