This paper explores and proves the twin prime conjecture. With the help of Excel's computing function, a number theoretic-IF function is proposed. The proof of twin prime conjecture is transformed into the evaluation problem of IF function. Excel is used to do a testability study on the increasing (undiminished) value of IF function. It is preliminarily proved that the value of IF function is non-zero and nondecreasing. If we further use mathematical mechanical proof, it is expected to solve the twin prime conjecture successfully.