This paper describes the technology of synthesizing alkylbenzenes containing C16–19 alkyl chains. The heavy alkylbenzenes were prepared by C16–19 liquid paraffin dehydrogenation, followed by alkylation with benzene. A novel catalyst containing Pt and Sn as its main components for the dehydrogenation of C16–19 paraffins to alkenes was prepared by vacuum impregnation and the catalyst exhibited high stability and selectivity. The alkylation of the C16–19 alkenes and benzene had a conversion yield of 86.15% and a selectivity of 81.21%. The main alkylbenzenes was identified as monoalkylbenzene by IR and chromatography analysis. C16–19 alkylbenzene sulfonates are found to give an ultra-low interfacial tension when mixing with crude oil/reservoir water.