Low-carbon olefine material is made to react under the conditions of temperature 160-220 deg.C, pressure 3.0-6.0 MPa and space velocity 1.0-4.0/hr to produce olefine of C6 and over by oligopolymerization or polyreaction in the presence of solid acid catalyst. Before reaction, the material and pre-treating agent in the volume ratio of 0.5-2 are made to flow into a static mixer for pre-treating with weak acid or water solution of alkali metal dihydric phosphate at temperature 40-60 deg.C, and the said method can eliminate alkali matter harmful to the catalyst inside the material to prolong lifeof the catalyst and may be used in industrial production.