Described herein is a novel series of multi-fluoro-substituted pyrazolopyrimidine compounds or salts thereof. These compounds are Bruton's tyrosine kinase (BTK) inhibitors. These compounds may possess better BTK inhibition selectivity and pharmacokinetic properties. Disclosed herein are the synthesis methods of these compounds. Disclosed herein are novel synthesis methods of the multi-fluoro-substituted benzophenone and substituted phenoxy benzene. Also disclosed are pharmaceutical compositions comprising the BTK inhibitors described herein. The present invention also relates to pharmaceutical formulations comprising the compounds described herein as active ingredients. The present invention also includes the therapeutic methods by administering the BTK inhibitors and their formulations to treat and inhibit autoimmune disease, hypersensitivity disease, inflammatory diseases and cancer.