The invention discloses a catalyst for oligomerization and polymerization of ethylene, which is a Fe<2+>, Co<2+>, Ni<2+>, Cr<3+>-containing halide of 2-(6'-imine pyridyl)benzothiazole. The invention also discloses a preparation method and application of the catalyst. The Fe<2+>, Co<2+>, Ni<2+>, Cr<3+>-containing halide of 2-(6'-imine pyridyl)benzothiazole serves as a main catalyst. Under the action of methylaluminoxane or diethyl aluminium chloride which is modified by different cocatalysts, the catalyst has relatively good ethylene oligomerization and/or polymerization catalytic performances, wherein an iron (II) coordination compound has very high oligomerization and polymerization activity for ethylene, which reaches 107g/mol Fe-1h-1. The oligomerization product includes C4, C6, C8, C10, C12, C14, C16, C18, C20 and C22 olefins and the like. The selectivity of alpha-olefin is up to 99 percent. The polymers are low-molecular weight olefins and polyolefins.