The invention provides a machine oil alarm joint leakage-proof structure comprising a connecting post, an insertion piece and a connecting piece member. The structure is characterized in that the insertion piece is connected to the connecting post; the insertion piece is provided with an insertion hole; the connecting member is arranged between the connecting post and the insertion piece; the connecting member is provided with a space-limiting plate; and a connecting block is arranged between the connecting post and the insertion piece. According to the invention, the connecting block is arranged between the connecting post and the insertion piece, and a sealing ring is arranged between the connecting member and the connecting block, so that the sealing performance between the connecting post and the insertion piece is improved through the connecting block; the leakage proof performance of a machine oil alarm joint is improved; the quality performance of the machine oil alarm joint is enhanced; the product quality of a machine oil alarm is further raised; the sealing performance between the connecting post and the insertion piece is further improved through the sealing ring; and the quality performance of the machine oil alarm joint is enhanced.