Japan should learn "profound lessons from history", China's defence ministry said after Japan's parliamentary vote.
The vote allows Japanese troops to fight overseas for the first time since the end of World War Two 70 years ago.
Tensions between China and Japan have escalated in recent months over a group of islands to which both lay claim.
The security laws were voted through Japan's upper house late on Friday, with 148 lawmakers voting in support and 90 against.
It followed nearly 200 hours of political wrangling, with scuffles breaking out at various points between the bills' supporters and opposition members attempting to delay the vote.
Compiled by BBC Monitoring
The government says that the changes in defence policy are vital to meet new military challenges such as those posed from a rising China.
But China's defence ministry said on Saturday they "run counter to the trend of the times that upholds peace, development and co-operation", the Xinhua news agency reports.
"The move has breached the restrictions of Japan's pacifist constitution," the ministry added.
Many Japanese who opposed the bills - which prompted large public protests - were also attached to the pacifist provisions in the constitution that banned fighting overseas.
China also urged Japan to "heed the security concern" of its Asian neighbours and do more to promote regional peace and stability.
South Korea, which also has a tense relationship with Japan, has warned Tokyo not to exercise the new defence laws without its approval.
But the US, Japan's ally, and the UK have both welcomed the changes.
UK Foreign Secretary Philip Hammond said he looked forward to Japan "taking an increasingly active part in peacekeeping operations".
Japan's post-World War Two constitution bars it from using force to resolve international conflicts except in cases of self-defence.
The new security legislation allows Japan's military to mobilise overseas when these three conditions are met:
What's behind Japan's military shift?
Critics say the changes violate the pacifist constitution and could lead Japan into US-led wars abroad.
Supporters of the measures insist they are essential for the defence of Japan and its regional allies, and will permit greater involvement in peacekeeping activities around the world.
Critics have focused on what they say is ambiguity in how the principles of the legislation will be interpreted, and the possibility that future governments will interpret them more broadly.
China has said Japan is endangering peace in the region after it passed controversial laws expanding the role of its military abroad.