Abstract: Ultra-long organic phosphorescent materials have the advantages of rich excited state properties, low price and easy to synthesize, good flexibility, ultra-long luminescence lifetime. After the fluorescence decay of the background, the collection of the remaining light can effectively eliminate the background light interference. Based on this, a Lateral Flow Immunochromatographic Detection Platform Based on Ultra-Long Organo-Phosphorescent Nanoprobes (UOP-LFIAs) constructed by authors is presented in this paper. Firstly, long afterglow crystals were prepared and synthesized, and then the long afterglow solution was obtained by one-step coating polyvinylpyrrolidone and carboxymethyl cellulose on the surface. Next, it was coupled with antibodies to obtain ultra-long organic afterglow phosphorescent nanoprobes. A portable UOP-LFIAs test strip detection analyzer was then designed and manufactured. Finally, Pepsinogen (PG) I and II were detected by using a portable UOP-LFIAs detection device. The results show that the detection limits were 0.36 ng/mL and 0.57 ng/mL for PG I and PG II, with respective detection ranges of 0.36-1200 ng/mL and 0.57-500 ng/mL. The average recoveries were 101.30% and 99.30%, respectively. It is concluded that the UOP-LFIAs assay platform established in this study is not only simple, rapid, cost-effective and suitable for macro-preparation, but also can effectively reduce the interference of background light signal and enhance the phosphorescence efficiency, thereby improving the detection sensitivity. Additionally, the platform enables the combined detection of PG I and PG II, providing results in just 5 minutes. This development offers a powerful tool for bedside disease detection.