The police officer was seen being handcuffed, held at gunpoint and beheaded, The Daily Mail reported on Wednesday.
The eight minute video also contains footage of militants attacking army barracks. The video shared on social media, is recorded in a similar style to barbaric videos released by ISIS over the last year.
Boko Haram pledged it allegiance to ISIS in March this year. The group is responsible for killing more than 10,000 people in Nigeria.
The video shows intense firefights in the day and night time on army barracks in Borno and Yobe.
Militants can be seen carrying AK-47s and are backed up by tanks and heavy weaponry.
The footage cuts to a scene with a man dressed in uniform - believed to be a policeman - who is then held down and beheaded by three jihadis.
The group has increasingly expanded its operations into neighbouring countries in recent months, prompting Nigeria, Cameroon, Chad and Niger to launch a coordinated military fightback.
Nigeria has seen increase in attacks carried out by the group since Nigeria's new President took office in May, unleashing a wave of violence that has claimed 800 lives in just two months.