The process of sucrose producing polyisoprene (rubber hydrocarbon) through a series of physiological and biochemical activities in the milk tube. The biosynthesis of rubber is carried out on the surface of rubber particles of laticifer cells. Rubber biosynthesis is a typical secondary metabolic pathway of isoprene in plants. Firstly, sucrose generates acetyl coenzyme A through glycolysis and tricarboxylic acid cycle. Pentose phosphate pathway produces reduced coenzyme II (NADPH), with NADPH as reducing agent and ATP generated by tricarboxylic acid cycle and glycolysis as energy source, mevalonate is generated from acetyl coenzyme A, and then isopentene pyrophosphate (IPP) is synthesized from mevalonate, and dimethyl propylene pyrophosphate (DMAPP) is generated under the catalysis of IPP isomerase. Isopentene pyrophosphate was added to dimethyl propylene pyrophosphate under the catalysis of rubber elongation factor (REF) and trans-isoprene transferase (TPT), and isoprene compounds such as C 10, C 15 and C20 were synthesized. Finally, under the catalysis of rubber transferase (RuT), isopentene pyrophosphate was added to isoprene compound to form rubber hydrocarbon.