The invention discloses an environment-friendly built-in sealant which is prepared from hydroxyl-terminated polydimethylsiloxane, hydrophobic silicon dioxide, vinyltriethoxysilane, butyl titanate, organic bismuth and the like. The invention also relates to a preparation method of the environment-friendly built-in sealant. According to the preparation method of the environment-friendly built-in sealant, the components are put into a reaction kettle in sequence and are fully stirred under the corresponding conditions. According to the method, the cured dealcoholized silicone sealant can be quickly prepared by adding the vinyltriethoxysilane and has a certain tensile strength in a short time, so that the decoration working efficiency and the quality guarantee can be effectively improved in the indoor decoration industry; by creatively adding butyl titanate and a supplemented organic ruthenium catalyst, the butyl titanate serves as a tackifier for improving polymer adhesion, not only provided rapid cross-linking reaction can be, but also the adhesion of a polymer system is improved, and the curing efficiency and the initial tensile strength in a short time can be further improved.