A multifunctional constant flow adjusting valve for fluid adjustment and automatic control comprises a valve body; the upper part of the valve body is provided with a valve cover; the lower part of the valve body is provided with a drain outlet; the center of the valve cover is provided with a valve shaft; the lower part of the valve shaft is provided with an adjusting valve clack; and a valve sleeve, a pressure difference sensor and a double-seat valve clack for pressure difference compensation are arranged inside the valve body to form a valve core. Compared with the prior art, the multifunctional constant flow adjusting valve is more compact and reasonable in structure, simple to disassemble and maintain, visual for flow display and rich in function, and can be applied to more fields.