The present invention provides a process for preparing cytisine from thermopsis lanceolata glasses or seeds. The process comprises: crushing thermopsis lanceolata glasses into coarse powder (1-3 cm) or breaking thermopsis lanceolata seeds, weighing a certain amount of thermopsis lanceolata glass coarse powder or broken thermopsis lanceolata seeds, adding an alkaline solution to moisten for 6-8 h, adding chloroform to carry out reflux extraction, mixing the extraction solutions, carrying out reduced pressure concentration to recover the chloroform, adding ethanol to dissolve, adopting a decoloration agent to carry out decoloration, filtering, carrying out reduced pressure recovery of ethanol, adding acetone to carry out crystallization to obtain a cytisine crude product, and adding petroleum ether to carry out re-crystallization to obtain the cytisine fine product. The process method has characteristics of simpleness, practicality, low cost and high purity, and is suitable for industrial production.