Yu-7 (鱼-7) torpedo is the Chinese development of the US Mk 46 Mod. 2 light ASW torpedo incorporating technologies of the A244-S torpedo. Many domestic Chinese sources have considered Yu-7 torpedo as the Chinese equivalent of US Mk 46 Mod. 3 torpedo.
According to official information released by the Chinese government, several US Mark 46 torpedoes had been recovered by Chinese fishermen in the 1970s and 1980s, with the most advanced version the Mk 46 Mod. 1 Block 2 torpedo recovered in October, 1978 from South China Sea. Decision was given to reverse engineer the American torpedo under the name “Project 109” to produce the badly needed ASW light torpedo for the Chinese military. 705th Institute (also called Xi'an Precision Machinery Research Institute, 西安精密机械研究所) and Northwestern Polytechnical University were tasked with being the research team, while the No. 872 Factory and No. 874 Factory were assigned as the production facility. Full scale development started in 1984, with over 90 enterprises in the country involved in assisting the four major enterprises to develop the torpedo. 705th Institute (also known as Xi'an Precision Machinery Research Institute, 西安精密机械研究所) was responsible for the shallow water control systems of the torpedo and Northwestern Polytechnical University was responsible for the deep water control systems of the torpedo. The Yu-7 torpedo is composed of over 5,000 parts and 4,500 instruments, while it had over 80,000 blueprints and its technical documents totaled over 100,000 pages. The first two prototype torpedoes were assembled in No. 874 Factory in December 1984 and were tested in the 750 Testing Range (750试验场) in Kunming in December 1985. By 1989 the Yu-7 torpedo had successfully undertaken 68 launches in four separate sea trials.
In the meantime, the development of Yu-7 torpedo obtained a great boost from USA technical support in 1985, when China signed a US$ 8 million deal with USA in purchasing Mk 46 Mod. 2 torpedoes with technological support for licensed assembly. The Bush Administration had faced significant criticism from congress and many human rights activist groups for delivering the last batch of Mk 46 Mod. 2 torpedo to China after the Tiananmen Square protests of 1989, but the Bush Administration countered that the delivery was the completion of a previous deal made prior to the crackdown. Another great benefit to the Yu-7 torpedo program was the Chinese purchase of 40 or so Italian Alenia A244-S light ASW torpedoes in 1987, with the 705th Institute assigned to reverse engineer this torpedo as well. The incorporation of technologies of the Italian Alenia A244-S light ASW torpedo caused design changes and thus delayed the schedule, but according the western sources such as Jane's Information Group, the biggest factor that caused the delay in the schedule was the difficulties encountered in converting the British system to the metric system and American Institute of Electrical and Electronics Engineers standards to international standards. The Yu-7 torpedo finally received certification in 1994 and went into full production in the late 1990s.
- Diameter: 324 mm
- Length: 2.6 m
- Weight: 235 kg
- Warhead: 45 kg
- Guidance: active / passive acoustic homing
- Propulsion: Otto fuel II
- Range: > 7.3+ km and better
- Speed: > 47+ kt and better 
- Depth: > 400+ m and better
- Sting Ray (torpedo) - British equivalent
- Mark 54 MAKO Lightweight Torpedo - US Navy's equivalent
- MU90 Impact - French equivalent
- APR-3E torpedo - Russian equivalent