Abstract: Substituted polydiacetylenes (PDAs) as nonlinear optical materials have manny advantages such as their higher nonlinear coefficients, rapid response and high damage threshold etc..So they are very useful in their application in optical devices. In this paper the synthesis of sir novel derivatives of 5-(2-methylthio-4-methyl-5-Pyrimidinyl)-2,4-pentadiyne-l-ol is reported.