In situations where testing is destructive or very expensive, small sample plans such as the chain sampling plan are used. The original chain sampling plan introduced by Dodge, known as the ChSP-1 plan, calls for the use of past lot inspection results when the current sample has a nonconforming unit. This selective use of related lot inspection results helps to achieve a more discriminating Operating Characteristic curve but it does not lead to a reduction in sample size... Thus, in order to achieve a smaller sample size, the approach for chaining the results of the i preceding lots may be modified. By considering this concept, a study on modified chain sampling plan is done .The modified chain sampling plan is developed using stochastical differential equation. In this procedure ,the fraction defective is a variable instesd of a constant.The plan is developed through minimum tangent angle criteria also. The table shows that at a point where the tangent angle is minimum, the sum of the risks is also minimum.