Li was one of the Chinese officials who willingly learned European astronomy, geography, mathematics, and Catholic doctrines from Matteo Ricci. Baptized Liang (Leon) by Ricci, Li converted to Catholicism upon the earnest persuasion of the critically ill Ricci one month before the latter's death (May 1610). Upon conversion, Li helped missionaries spread the Gospel to his native home and sheltered them during precarious times when they came under suspicion and were rejected by other Chinese officials. He helped the missionaries with their translation work by polishing up their Chinese and did some writing himself to propagate Catholicism. Li, Xu Guangqi, and Yang Tingjun are considered the three pillars of the early Chinese Catholic Church.