This study is a single-arm, open-label, single-dose, dose-escalation trial, aiming to evaluate the safety and tolerability of YOLT-203 in the Chinese population with type 1 primary hyperoxaluria (PH1); and to preliminarily assess the effect of a single dose of YOLT-203 on the plasma oxalate level. In this study, the maximum screening period of the main study is 60 days, the treatment day is Day 1 (D1), and the safety follow-up period is up to Week 52 after administration. In addition, subjects within the first dose group can voluntarily receive a second treatment with the test drug at the effective dose level. After the end of the main study, the subjects will undergo long-term follow-up. According to the requirements of the "Technical Guidelines for Long-Term Follow-up Clinical Studies of Gene Therapy Products (Trial)" issued by the CDE, the long-term follow-up is up to 15 years after administration.