The number of violation cases that occurred in distribution activity of LPG 3 kg from agent to LPG agent’s base, caused PT. Pertamina made an innovation to facilitate the monitoring and selling price monitoring at the agent level to the agent’s base with the non-cash payment or Cashless Payment program. LPG agent's base participation through socialization will determine the success of PT. Pertamina's program, whether the LPG agent's base will still use the cashless payment method or switch to use the cash payment method. In order to make LPG agent's base to switch using cashless payment Influence of Understanding Level of Socialization Messages on Level of LPG Agent Participation Base in Cashless Payment Program PT. Pertamina (Persero) Branch Marketing DIY & Surakarta in Yogyakarta City. Therefore it is necessary to identify how the influence of understanding of Cashless Payment socialization message and level of participation of LPG agent base in Yogyakarta City. The research methodology used is explanative research with Likert scale as data collection techniques which is 90 amount of questionnaires that already distributed. Data analysis in this research using validity test, reliability test, and simple linear regression analysis. The results of this study indicated that the cashless payment method has a positive effect on the participation of the LPG agent base at 0.335 and the significance value of 0.00. The result of simple linear regression analysis showed that the decision of LPG agent base in using cashless payment method is influenced by 1 variable that is understanding of socialization message cashless payment 32,1%, the rest is 67,9% agent base do use method of cashless payment.