A solid acid catalyst has a macropore specific volume of about 0.30-0.50 ml/g, a ratio of macropore specific volume to specific length of catalyst particles of about 1.0-2.5 ml/(g·mm), and a ratio of specific surface area to length of catalyst particles of about 3.40-4.50 m2/mm. The macropore refers to pores having a diameter of more than 50 nm. An alkylation catalyst is based on the solid acid catalyst and can be used in alkylation reactions. The solid acid catalyst and alkylation catalyst show an improved catalyst service life and/or trimethylpentane selectivity when used in the alkylation of isoparaffins with olefins.