The title compound (E)-2-(2-(4,8,8-trimethyldecahydro-1,4-methanoazulen-9-ylidene)ethyl)ben-zo[d]isothiazol-3(2H)-one (Ic) was synthesized from longifolene and 1,2-benzoisothiazolinone (short as BIT) through Prins,halogenation and nitro-alkylation reaction and structurally identified by means of HRMS,IR,1H-NMR,13C-NMR and single-crystal X-ray diffraction.The crystal of compound Ic is of bi-molecular structure and belongs to orthorhombic system,P212121 space group with a =7.5715(7),b =16.8824(9),c =31.1926(14) (A),V =3987.2(5) (A)3,Mr =367.53,Dc =1.225 mg/m3,Z =8,μ =0.174 mm-1 and F(000) =1584.A total of 17045 reflections were collected,of which 7306 were unique (Rat =0.0566).The structure was refined to R =0.0967 and wR =0.1998 for 7306 observed reflections with Ⅰ ＞ 2σ(Ⅰ).1D chain along the a-axis is formed by two types of π-π interactions between benzene rings from adjacent molecules.Especially,compound Ic shows improved solubility in nonpolar organic solvents and higher antimicrobial activity than longifolene and BIT against bacteria and fungi.The minimum inhibition concentration (MIC) of Ic against two Gram-positive bacteria (S.aureus and B.subtili),two Gram-negative bacteria (E.coli and K.pneumoniae) and three fungi (C.albicans,C.tropicalis and A.niger) are 0.242,0.242,15.6,15.6,1.95,1.95 and 1.95 μg/mL,respectively.