While finding escape velocity, does human mass counts as the mass of Earth? Escape velocity depends upon the mass of earth. my doubt is whether human mass adds into it or not? If it add then Earth's escape velocity would be increasing!
 A: Yes you need to include the mass of the 7 billion or so humans in the total mass of the Earth, though since their total mass is something like $5 \times 10^{11}$kg and the mass of the Earth is around $6 \times 10^{24}$kg humans make up only about 0.00000000001% of the total mass. We don't make any great contribution to the escape velocity.
The point of your second sentence is presumably that as the number of humans increases their total mass increases. This is true, but humans are basically created from carbon dioxide and water (courtesy of plants) so an increase in the number of humans means a corresponding decrease in the mass of carbon dioxide and water. The total mass of the Earth + humans doesn't change.
A: No, you don't need to account for the mass of humans. We're a part of the total mass. Children who grow and gain weight are merely transferring mass from other parts of the Earth to them. The mass of humanity versus the mass of everything else on the Earth is a zero sum game.
To see whether the Earth is changing mass, you need to look outside the box (or in this case, outside the Earth). Imagine a spherical boundary 10,000 kilometers above the surface of the Earth. Some stuff, mostly hydrogen, crosses that boundary from inside to outside. This represents mass lost to the universe. Other stuff, mostly tiny little meteorites, crosses that boundary from outside to inside. This represents mass gained from the universe.
The estimated loss in mass due to escaping hydrogen is estimated to be about 260 metric tons per day. The estimates in how much the Earth is gaining mass due to incoming meteorites and space dust vary widely, from a mere 5 metric tons per day to over 300 metric tons per day. The lower figure means the Earth loses about 255 metric tons of mass every day. The upper figure means the Earth gains about 40 metric tons per day.
Those numbers sound large, but compared to the total mass of the Earth, they are very small.
A: There is approximately 7 billion people on earth. If we take some average of about 75 kg each, that means
$$
m_{\rm population}=7\cdot10^9\times75\,{\rm kg}=5.25\cdot10^{11}\,{\rm kg}
$$
The mass of the earth is roughly
$$
m_{\rm earth}=5.97\cdot10^{24}\,{\rm kg}
$$
which is about 13 orders of magnitude bigger than the total population of the world. So no, the population of earth is irrelevant to the escape velocity of earth.
