The invention relates to a flexible hydrogel microneedle patch and a preparation method thereof. The microneedle patch includes a microneedle substrate layer, a heating layer, a drug barrier layer anda drug storage layer. The microneedle substrate layer comprises a flexible substrate and hydrogel needle bodies penetrating the flexible substrate; the drug barrier layer consists of thermotropic phase change materials and covers the tops of the hydrogel needle bodies; the heating layer is arranged between the microneedle substrate layer and the drug barrier layer and used for heating the drug barrier layer; one surface of the drug storage layer is bonded with the drug barrier layer and provided with a groove, a drug solution is stored in the groove, and the groove and at least one hydrogel needle body form a drug solution channel after the drug barrier layer is converted into a liquid state through heating. The thermotropic phase change materials are used to serve as the drug barrier layer, flexible polymer materials are used for preparing the flexible substrate, and the flexible hydrogel microneedle patch can achieve controlled release of the drug solution according to the need, fits the skin of the human body and makes people feel comfortable.