Am I eligible to apply for MBBS course in AFMC after completion of B.Pharma at the age of 21 year???

Yes, you are eligible for MBBS in AFMC after B.Pharma at age 21 as its minimum eligibility states that you must have passed XII Standard and you must bit have attain the age of 22 years

AFMC MBBS Eligibility
-You should be a citizen of India or be a subject of Nepal or Bhutan or a person of Indian origin migrated from Pakistan or any other foreign country with the intention of permanently settling in India.
-Must be unmarried. Marrying during the course is not permitted.
0Should be medically fit as per prescribed standards by the Govt. of India, Ministry of Defence

Academic Qualifications
-Must have passed the XII standard/pre-professional/premedical examination or equivalent examination of statutory Indian University/Board or any other recognized Board/University as a regular student in all the subjects opted for in FIRST ATTEMPT with the subjects of English, Physics, Chemistry and Biology securing minimum 60% of aggregate marks in the three science subjects taken together, minimum 50% marks in each of the science subjects and not less than 50% marks in English.
-They must have also passed an examination in Mathematics at least of the matriculation standard.
-A graduate of B.Sc. Examination with not less than two of the subjects Physics, Chemistry, Biology (Botany or Zoology) and also must have passed the earlier qualifying examination i.e. XII standard/Pre professional (Med) with Physics, Chemistry, Biology and English and obtained marks as stated above.

Age
-Must have attained the age of 17 years but must NOT have attained the age of 22 years