The invention discloses an adjustable spray nozzle assembly for a 3D printer, the adjustable spray nozzle assembly comprises a thermal insulation mechanism, a heat dissipation mechanism, a material guiding pipe, a heating block, a spray nozzle, an adjusting mechanism and a circular disc, the thermal insulation mechanism comprises an upper pipe, a middle pipe and a lower pipe, the heat dissipation mechanism comprises a heat dissipation pipe, heat dissipation pieces and a groove, the upper pipe and the heat dissipation pipe are in screwed connection, one end of the material guiding pipe is attached to a shrink mouth, the other end of the material guiding pipe abuts on the upper surface of the middle pipe, the lower pipe and the heating block are in screwed connection, the spray nozzle comprises a screwing part and a sliding part, the screwing part and the heating block are in screwed connection, the adjusting mechanism includes an inverted T shaped rod; the circular disc includes an accommodating tank and a storage tank, the center of the bottom surface of the storage tank is provided with a plurality of extrusion holes, the upper end of the accommodating tank shrinks inward to form a shrinking part with a clamping opening, an upper thread hole cooperated with a lower thread hole of the screwing part is arranged on the shrinking part located above each extrusion hole, and when the spray nozzle and the circular disc are in screwed fixing, the center hole of the sliding part and one of the extrusion hole are in alignment. The adjustable spray nozzle assembly has the advantages of effective diffusion of heat transferred to the heat dissipation pipe, and by matched use of the spray nozzle and the adjusting mechanism, the pore size of the spray nozzle can be adjusted.