This STEM project is to simulate the Poker Probability. The game rule is to select three from four shared cards plus two own cards to form the BEST Five to determine who can be the winner. In order to simplify the probability scenario, partial deck (9, 10, J, Q, K, and A) are drawn to increase matching probability on higher ranked patterns such as Four of a Kind and Full House. Author used JAVA random simulation method and conducted Combination and Conditional Probability to calculate each player’s winning probability. Author used a simple case study to derive the winning probability between two players. JAVA random simulation is programmed to generate the random cards for both players. JAVA programming can randomly duplicate the real Poker scenario in a random way to distribute the cards to players randomly. Authors compared the JAVA simulated results against the expected probability derived based on combination and conditional probability. Contingency table, Chi-Square proportions tests were conducted and confirmed that the JAVA simulated probability could match the expected Poker probability very well. This is a very successful STEM project which has integrated JAVA Computer Science and Statistics/Probability on the Poker application.